go Documentation

Technical Documentation: golang/go

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Overview (README.md) Copy Section

The Go Programming Language

Go is an open source programming language that makes it easy to build simple,
reliable, and efficient software.

Gopher image by Renee French, licensed under Creative Commons 4.0 Attribution license.

Our canonical Git repository is located at https://go.googlesource.com/go.
There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the
BSD-style license found in the LICENSE file.

Download and Install Copy Section

Binary Distributions

Official binary distributions are available at https://go.dev/dl/.

After downloading a binary release, visit https://go.dev/doc/install
for installation instructions.

Install From Source

If a binary distribution is not available for your combination of
operating system and architecture, visit
https://go.dev/doc/install/source
for source installation instructions.

Contributing Copy Section

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines at https://go.dev/doc/contribute.

Note that the Go project uses the issue tracker for bug reports and
proposals only. See https://go.dev/wiki/Questions for a list of
places to ask questions about the Go language.

Doc README (`doc/README.md`) Copy Section

Release Notes

The initial and next subdirectories of this directory are for release notes.

For developers Copy Chapter

Release notes should be added to next by editing existing files or creating
new files. Do not add RELNOTE=yes comments in CLs. Instead, add a file to
the CL (or ask the author to do so).

At the end of the development cycle, the files will be merged by being
concatenated in sorted order by pathname. Files in the directory matching the
glob "*stdlib/*minor" are treated specially. They should be in subdirectories
corresponding to standard library package paths, and headings for those package
paths will be generated automatically.

Files in this repo's api/next directory must have corresponding files in
doc/next/*stdlib/*minor.
The files should be in the subdirectory for the package with the new
API, and should be named after the issue number of the API proposal.
For example, if the directory 6-stdlib/99-minor is present,
then an api/next file with the line

pkg net/http, function F #12345

should have a corresponding file named doc/next/6-stdlib/99-minor/net/http/12345.md.
At a minimum, that file should contain either a full sentence or a TODO,
ideally referring to a person with the responsibility to complete the note.

If your CL addresses an accepted proposal, mention the proposal issue number in
your release note in the form /issue/NUMBER. A link to the issue in the text
will have this form (see below). If you don't want to mention the issue in the
text, add it as a comment:

If an accepted proposal is mentioned in a CL but not in the release notes, it will be
flagged as a TODO by the automated tooling. That is true even for proposals that add API.

Use the following forms in your markdown:

[http.Request]                     # symbol documentation; auto-linked as in Go doc strings
[Request]                          # short form, for symbols in the package being documented
[net/http]                         # package link
[#12345](/issue/12345)             # GitHub issues
[CL 6789](/cl/6789)                # Gerrit changelists

To preview next content in merged form using a local instance of the website, run:

go run golang.org/x/website/cmd/golangorg@latest -goroot=..

Then open http://localhost:6060/doc/next. Refresh the page to see your latest edits.

For the release team Copy Chapter

The relnote tool, at golang.org/x/build/cmd/relnote, operates on the files
in doc/next.

As a release cycle nears completion, run relnote todo to get a list of
unfinished release note work.

To prepare the release notes for a release, run relnote generate.
That will merge the .md files in next into a single file.
Atomically (as close to it as possible) add that file to _content/doc directory
of the website repository and remove the doc/next directory in this repository.

To begin the next release development cycle, populate the contents of next
with those of initial. From the repo root:

> cd doc
> cp -R initial/ next

Then edit next/1-intro.md to refer to the next version.

Doc Initial 1 Intro (`doc/initial/1-intro.md`) Copy Section

DRAFT RELEASE NOTES — Introduction to Go 1.N {#introduction} Copy Chapter

Go 1.N is not yet released. These are work-in-progress release notes.
Go 1.N is expected to be released in {Month} {Year}.

Doc Next 1 Intro (`doc/next/1-intro.md`) Copy Section

DRAFT RELEASE NOTES — Introduction to Go 1.28 {#introduction} Copy Chapter

Go 1.28 is not yet released. These are work-in-progress release notes.
Go 1.28 is expected to be released in February 2027.

Src Go Doc Comment Testdata README (`src/go/doc/comment/testdata/README.md`) Copy Section

This directory contains test files (*.txt) for the comment parser.

The files are in txtar format.
Consider this example:

-- input --
Hello.
-- gofmt --
Hello.
-- html --
Hello.
-- markdown --
Hello.
-- text --
Hello.

Each -- name -- line introduces a new file with the given name.
The file named “input” must be first and contains the input to
comment.Parser.

The remaining files contain the expected output for the named format generated by
comment.Printer:
“gofmt” for Printer.Comment (Go comment format, as used by gofmt),
“html” for Printer.HTML, “markdown” for Printer.Markdown, and “text” for Printer.Text.
The format can also be “dump” for a textual dump of the raw data structures.

The text before the -- input -- line, if present, is JSON to be unmarshaled
to initialize a comment.Printer. For example, this test case sets the Printer's
TextWidth field to 20:

{"TextWidth": 20}
-- input --
Package gob manages streams of gobs - binary values exchanged between an
Encoder (transmitter) and a Decoder (receiver).
-- text --
Package gob
manages streams
of gobs - binary
values exchanged
between an Encoder
(transmitter) and a
Decoder (receiver).

Src Go Doc Testdata Examples README (`src/go/doc/testdata/examples/README.md`) Copy Section

These files are processed by example_test.go:TestExamples.

A .golden file is a txtar file with two sections for each example that should be
created by doc.Examples from the corresponding .go file.

One section, named EXAMPLE_NAME.Output, contains the example's output,
the value of the field Example.Output.

The other, named EXAMPLE_NAME.Play, contains the formatted code for a playable
version of the example, the value of the field Example.Play.

If a section is missing, it is treated as being empty.

Doc Godebug (`doc/godebug.md`) Copy Section

title: "Go, Backwards Compatibility, and GODEBUG" layout: article Copy Chapter

Introduction {#intro} Copy Chapter

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.
If code depends on buggy (including insecure) behavior,
then fixing the bug will break that code.
New features can also have similar impacts:
enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and
permitted by the Go 1 compatibility rules.
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a key=value pair
that controls the execution of certain parts of a Go program.
The environment variable GODEBUG
can hold a comma-separated list of these settings.
For example, if a Go program is running in an environment that contains

GODEBUG=http2client=0,http2server=0

then that Go program will disable the use of HTTP/2 by default in both
the HTTP client and the HTTP server.
Unrecognized settings in the GODEBUG environment variable are ignored.
It is also possible to set the default GODEBUG for a given program
(discussed below).

When preparing any change that is permitted by Go 1 compatibility
but may nonetheless break some existing programs,
we first engineer the change to keep as many existing programs working as possible.
For the remaining programs,
we define a new GODEBUG setting that
allows individual programs to opt back in to the old behavior.
A GODEBUG setting may not be added if doing so is infeasible,
but that should be extremely rare.

GODEBUG settings added for compatibility will be maintained
for a minimum of two years (four Go releases).
Some, such as http2client and http2server,
will be maintained much longer, even indefinitely.

When possible, each GODEBUG setting has an associated
runtime/metrics counter
named /godebug/non-default-behavior/<name>:events
that counts the number of times a particular program's
behavior has changed based on a non-default value
for that setting.
For example, when GODEBUG=http2client=0 is set,
/godebug/non-default-behavior/http2client:events
counts the number of HTTP transports that the program
has configured without HTTP/2 support.

Default GODEBUG Values {#default} Copy Chapter

When a GODEBUG setting is not listed in the environment variable,
its value is derived from three sources:
the defaults for the Go toolchain used to build the program,
amended to match the Go version listed in go.mod,
and then overridden by explicit //go:debug lines in the program.

The GODEBUG History gives the exact defaults for each Go toolchain version.
For example, Go 1.21 introduces the panicnil setting,
controlling whether panic(nil) is allowed;
it defaults to panicnil=0, making panic(nil) a run-time error.
Using panicnil=1 restores the behavior of Go 1.20 and earlier.

When compiling a work module or workspace that declares
an older Go version, the Go toolchain amends its defaults
to match that older Go version as closely as possible.
For example, when a Go 1.21 toolchain compiles a program,
if the work module's go.mod or the workspace's go.work
says go 1.20, then the program defaults to panicnil=1,
matching Go 1.20 instead of Go 1.21.

As an exception, GODEBUGs introduced for security releases
will have the new behavior apply to all versions.

Because this method of setting GODEBUG defaults was introduced only in Go 1.21,
programs listing versions of Go earlier than Go 1.20 are configured to match Go 1.20,
not the older version.

To override these defaults, starting in Go 1.23, the work module's go.mod
or the workspace's go.work can list one or more godebug lines:

godebug (
	default=go1.21
	panicnil=1
	asynctimerchan=0
)

The special key default indicates a Go version to take unspecified
settings from. This allows setting the GODEBUG defaults separately
from the Go language version in the module.
In this example, the program is asking for Go 1.21 semantics and
then asking for the old pre-Go 1.21 panic(nil) behavior and the
new Go 1.23 asynctimerchan=0 behavior.

Only the work module's go.mod is consulted for godebug directives.
Any directives in required dependency modules are ignored.
It is an error to list a godebug with an unrecognized setting.
(Toolchains older than Go 1.23 reject all godebug lines, since they do not
understand godebug at all.) When a workspace is in use, godebug
directives in go.mod files are ignored, and go.work will be consulted
for godebug directives instead.

The defaults from the go and godebug lines apply to all main
packages that are built. For more fine-grained control,
starting in Go 1.21, a main package's source files
can include one or more //go:debug directives at the top of the file
(preceding the package statement).
The godebug lines in the previous example would be written:

//go:debug default=go1.21
//go:debug panicnil=1
//go:debug asynctimerchan=0

Starting in Go 1.21, the Go toolchain treats a //go:debug directive
with an unrecognized GODEBUG setting as an invalid program.
Programs with more than one //go:debug line for a given setting
are also treated as invalid.
(Older toolchains ignore //go:debug directives entirely.)

The defaults that will be compiled into a main package
are reported by the command:

go list -f '{{.DefaultGODEBUG}}' my/main/package

Only differences from the base Go toolchain defaults are reported.

When testing a package, //go:debug lines in the *_test.go
files are treated as directives for the test's main package.
In any other context, //go:debug lines are ignored by the toolchain;
go vet reports such lines as misplaced.

GODEBUG History {#history} Copy Chapter

This section documents the GODEBUG settings introduced and removed in each major Go release
for compatibility reasons.
Packages or programs may define additional settings for internal debugging purposes;
for example,
see the runtime documentation
and the go command documentation.

Go 1.28 Copy Section

Go 1.28 changed
net/http.FileServer,
net/http.FileServerFS,
net/http.ServeContent,
net/http.ServeFile, and
net/http.ServeFileFS to
limit the maximum number of ranges in a Range header.
When the number of ranges in a header exceeds the new
httpservecontentmaxranges setting, the header is ignored.
The default value is httpservecontentmaxranges=200.
Setting httpservecontentmaxranges=0 disables the limit.
To avoid denial of service attacks, this setting and default
was backported to Go 1.27.2 and Go 1.26.9.

Go 1.28 added a new netmarshal setting that controls whether
the text marshaling of the types net.IPMask, net.IPNet, and
net.HardwareAddr is readable. The value netmarshal=0 will
JSON encode those types using an unreadable base64 encoding.
The value netmarshal=1 will use a readable version such as the IP address.
For Go 1.28 and 1.29 the default value remains netmarshal=0.
This ensures that JSON or other marshaled data generated by those
versions will be readable by older versions of Go.
The expectation is that Go 1.30 will change the default to be netmarshal=1.
Go 1.28 and all future releases will support both the old and new
encodings when reading data. This setting may be removed in a future Go release,
Go 1.34 at the earliest.

Go 1.27 Copy Section

Go 1.27 removed the gotypesalias setting, as noted in the Go 1.22 section.

Go 1.27 removed the tlsunsafeekm setting, as noted in the Go 1.22 section.

Go 1.27 removed the tlsrsakex setting, as noted in the Go 1.22 section.

Go 1.27 removed the tls3des setting, as noted in the Go 1.23 section.

Go 1.27 removed the tls10server setting, as noted in the Go 1.22 section.

Go 1.27 removed the x509keypairleaf setting, as noted in the Go 1.23 section.

Go 1.27 removed the asynctimerchan setting, as noted in the Go 1.23 section.

Go 1.27 added a new htmlmetacontenturlescape setting that controls whether
html/template will escape URLs in the url= portion of the content attribute of
HTML meta tags. The default htmlmetacontentescape=1 will cause URLs to be
escaped. Setting htmlmetacontentescape=0 disables this behavior. To avoid
content injection attacks, this setting and default was backported to Go 1.25.8
and Go 1.26.1.

Go 1.27 changes the default for tracebacklabels (added in Go 1.26)
to 1. This opt-out is expected to be kept indefinitely in case goroutine
labels acquire sensitive information that shouldn't be made available in
tracebacks.

Go 1.27 added a new x509sslcertoverrideplatform setting that controls whether
crypto/x509 will load roots from disk on Windows and Darwin when SSL_CERT_FILE
or SSL_CERT_DIR are set. The default value x509sslcertoverrideplatform=1 will
cause roots to be loaded from disk when these environment variables are set.
Setting x509sslcertoverrideplatform=0 disables this behavior in favor of using
the platform certificate store instead of honoring the environment variables. We
plan to remove this setting in Go 1.31.

Go 1.27 added a fips140ems setting that when set to 0 disables the
enforcement of Extended Master Secret in FIPS 140-3 mode. There is no change in
default behavior. This setting was backported to Go 1.26.6 and Go 1.25.13.
We plan to remove this setting in Go 1.31.

Go 1.26 Copy Section

Go 1.26 added a new httpcookiemaxnum setting that controls the maximum number
of cookies that net/http will accept when parsing HTTP headers. If the number of
cookies in a header exceeds the number set in httpcookiemaxnum, cookie parsing
will fail early. The default value is httpcookiemaxnum=3000. Setting
httpcookiemaxnum=0 will allow the cookie parsing to accept an indefinite
number of cookies. To avoid denial of service attacks, this setting and default
was backported to Go 1.25.2 and Go 1.24.8.

Go 1.26 added a new urlmaxqueryparams setting that controls the maximum number
of query parameters that net/url will accept when parsing a URL-encoded query string.
If the number of parameters exceeds the number set in urlmaxqueryparams,
parsing will fail early. The default value is urlmaxqueryparams=10000.
Setting urlmaxqueryparams=0 disables the limit. To avoid denial of service
attacks, this setting and default was backported to Go 1.25.6 and Go 1.24.12.

Go 1.26 added a new urlstrictcolons setting that controls whether net/url.Parse
allows malformed hostnames containing colons outside of a bracketed IPv6 address.
The default urlstrictcolons=1 rejects URLs such as http://localhost:1:2 or http://::1/.
Colons are permitted as part of a bracketed IPv6 address, such as http://[::1]/.
Go 1.27 limited this validation to http and https URLs, so the setting has no
effect on URLs with other schemes.

Go 1.26 enabled two additional post-quantum key exchange mechanisms:
SecP256r1MLKEM768 and SecP384r1MLKEM1024. The default can be reverted using the
tlssecpmlkem setting.

Go 1.26 added a new tracebacklabels setting that controls the inclusion of
goroutine labels set through the runtime/pprof package. Setting tracebacklabels=1
includes these key/value pairs in the goroutine status header of runtime
tracebacks and debug=2 runtime/pprof stack dumps. This format may change in the future.
(see go.dev/issue/76349)

Go 1.26 added a new cryptocustomrand setting that controls whether most crypto/...
APIs ignore the random io.Reader parameter. For Go 1.26, it defaults
to cryptocustomrand=0, ignoring the random parameters. Using cryptocustomrand=1
reverts to the pre-Go 1.26 behavior.

Go 1.25 Copy Section

Go 1.25 added a new decoratemappings setting that controls whether the Go
runtime annotates OS anonymous memory mappings with context about their
purpose. These annotations appear in /proc/self/maps and /proc/self/smaps as
"[anon: Go: ...]". This setting is only used on Linux. For Go 1.25, it defaults
to decoratemappings=1, enabling annotations. Using decoratemappings=0
reverts to the pre-Go 1.25 behavior. This setting is fixed at program startup
time, and can't be modified by changing the GODEBUG environment variable
after the program starts.

Go 1.25 added a new embedfollowsymlinks setting that controls whether the
Go command will follow symlinks to regular files embedding files.
The default value embedfollowsymlinks=0 does not allow following
symlinks. embedfollowsymlinks=1 will allow following symlinks.

Go 1.25 added a new containermaxprocs setting that controls whether the Go
runtime will consider cgroup CPU limits when setting the default GOMAXPROCS.
The default value containermaxprocs=1 will use cgroup limits in addition to
the total logical CPU count and CPU affinity. containermaxprocs=0 will
disable consideration of cgroup limits. This setting only affects Linux.

Go 1.25 added a new updatemaxprocs setting that controls whether the Go
runtime will periodically update GOMAXPROCS for new CPU affinity or cgroup
limits. The default value updatemaxprocs=1 will enable periodic updates.
updatemaxprocs=0 will disable periodic updates.

Go 1.25 disabled SHA-1 signature algorithms in TLS 1.2 according to RFC 9155.
The default can be reverted using the tlssha1=1 setting.

Go 1.25 switched to SHA-256 to fill in missing SubjectKeyId in
crypto/x509.CreateCertificate. The setting x509sha256skid=0 reverts to SHA-1.

Go 1.25 corrected the semantics of contention reports for runtime-internal locks,
and so removed the runtimecontentionstacks setting.

Go 1.25 (starting with Go 1.25 RC 2) disabled build information stamping when
multiple VCS are detected due to concerns around VCS injection attacks. This
behavior and setting was backported to Go 1.24.5 and Go 1.23.11. This behavior
can be renabled with the setting allowmultiplevcs=1.

Go 1.24 Copy Section

Go 1.24 added a new fips140 setting that controls whether the Go
Cryptographic Module operates in FIPS 140-3 mode.
The possible values are:

• "off": no special support for FIPS 140-3 mode. This is the default.
• "on": the Go Cryptographic Module operates in FIPS 140-3 mode.
• "only": like "on", but cryptographic algorithms not approved by
  FIPS 140-3 return an error or panic.
  For more information, see FIPS 140-3 Compliance.
  This setting is fixed at program startup time, and can't be modified
  by changing the GODEBUG environment variable after the program starts.

Go 1.24 changed the global math/rand.Seed to be a
no-op. This behavior is controlled by the randseednop setting.
For Go 1.24 it defaults to randseednop=1.
Using randseednop=0 reverts to the pre-Go 1.24 behavior.

Go 1.24 added new values for the multipathtcp setting.
The possible values for multipathtcp are now:

• "0": disable MPTCP on dialers and listeners by default
• "1": enable MPTCP on dialers and listeners by default
• "2": enable MPTCP on listeners only by default
• "3": enable MPTCP on dialers only by default

For Go 1.24, it now defaults to multipathtcp="2", thus
enabled by default on listeners. Using multipathtcp="0" reverts to the
pre-Go 1.24 behavior.

Go 1.24 changed the behavior of go test -json to emit build errors as JSON
instead of text.
These new JSON events are distinguished by new Action values,
but can still cause problems with CI systems that aren't robust to these events.
This behavior can be controlled with the gotestjsonbuildtext setting.
Using gotestjsonbuildtext=1 restores the 1.23 behavior.
This setting will be removed in a future release, Go 1.28 at the earliest.

Go 1.24 changed crypto/rsa to require RSA keys to be at
least 1024 bits. This behavior can be controlled with the rsa1024min setting.
Using rsa1024min=0 restores the Go 1.23 behavior.

Go 1.24 introduced a mechanism for enabling platform specific Data Independent
Timing (DIT) modes in the crypto/subtle package. This
mode can be enabled for an entire program with the dataindependenttiming setting.
For Go 1.24 it defaults to dataindependenttiming=0. There is no change in default
behavior from Go 1.23 when dataindependenttiming is unset.
Using dataindependenttiming=1 enables the DIT mode for the entire Go program.
When enabled, DIT will be enabled when calling into C from Go. When enabled,
calling into Go code from C will enable DIT, and disable it before returning to
C if it was not enabled when Go code was entered.
This currently only affects arm64 programs. For all other platforms it is a no-op.

Go 1.24 removed the x509sha1 setting. crypto/x509 no longer supports verifying
signatures on certificates that use SHA-1 based signature algorithms.

Go 1.24 changes the default value of the x509usepolicies
setting. from 0 to 1. When marshalling
certificates, policies are now taken from the
Certificate.Policies field rather
than the
Certificate.PolicyIdentifiers
field by default.

Go 1.24 enabled the post-quantum key exchange mechanism
X25519MLKEM768 by default. The default can be reverted using the
tlsmlkem setting.
This can be useful when dealing with buggy TLS servers that do not handle large records correctly,
causing a timeout during the handshake (see TLS post-quantum TL;DR fail).
Go 1.24 also removed X25519Kyber768Draft00 and the Go 1.23 tlskyber setting.

Go 1.24 made ParsePKCS1PrivateKey
use and validate the CRT parameters in the encoded private key. This behavior
can be controlled with the x509rsacrt setting. Using x509rsacrt=0 restores
the Go 1.23 behavior.

Go 1.23 Copy Section

Go 1.23 changed the channels created by package time to be unbuffered
(synchronous), which makes correct use of the Timer.Stop
and Timer.Reset method results much easier.
The asynctimerchan setting disables this change.
There are no runtime metrics for this change.
This setting will be removed in Go 1.27.

Go 1.23 changed the mode bits reported by os.Lstat and os.Stat
for reparse points, which can be controlled with the winsymlink setting.
As of Go 1.23 (winsymlink=1), mount points no longer have os.ModeSymlink
set, and reparse points that are not symlinks, Unix sockets, or dedup files now
always have os.ModeIrregular set. As a result of these changes,
filepath.EvalSymlinks no longer evaluates
mount points, which was a source of many inconsistencies and bugs.
At previous versions (winsymlink=0), mount points are treated as symlinks,
and other reparse points with non-default os.ModeType bits
(such as os.ModeDir) do not have the ModeIrregular bit set.

Go 1.23 changed os.Readlink and filepath.EvalSymlinks
to avoid trying to normalize volumes to drive letters, which was not always even possible.
This behavior is controlled by the winreadlinkvolume setting.
For Go 1.23, it defaults to winreadlinkvolume=1.
Previous versions default to winreadlinkvolume=0.

Go 1.23 enabled the experimental post-quantum key exchange mechanism
X25519Kyber768Draft00 by default. The default can be reverted using the
tlskyber setting.
This can be useful when dealing with buggy TLS servers that do not handle large records correctly,
causing a timeout during the handshake (see TLS post-quantum TL;DR fail).

Go 1.23 changed the behavior of
crypto/x509.ParseCertificate to reject
serial numbers that are negative. This change can be reverted with
the x509negativeserial setting.

Go 1.23 re-enabled support in html/template for ECMAScript 6 template literals by default.
The jstmpllitinterp setting no longer has
any effect.

Go 1.23 changed the default TLS cipher suites used by clients and servers when
not explicitly configured, removing 3DES cipher suites. The default can be reverted
using the tls3des setting.
This setting will be removed in Go 1.27.

Go 1.23 changed the behavior of tls.X509KeyPair
and tls.LoadX509KeyPair to populate the
Leaf field of the returned tls.Certificate.
This behavior is controlled by the x509keypairleaf setting. For Go 1.23, it
defaults to x509keypairleaf=1. Previous versions default to
x509keypairleaf=0.
This setting will be removed in Go 1.27.

Go 1.23 changed
net/http.ServeContent,
net/http.ServeFile, and
net/http.ServeFS to
remove Cache-Control, Content-Encoding, Etag, and Last-Modified headers
when serving an error. This behavior is controlled by
the httpservecontentkeepheaders setting.
Using httpservecontentkeepheaders=1 restores the pre-Go 1.23 behavior.

Go 1.22 Copy Section

Go 1.22 adds a configurable limit to control the maximum acceptable RSA key size
that can be used in TLS handshakes, controlled by the tlsmaxrsasize setting.
The default is tlsmaxrsasize=8192, limiting RSA to 8192-bit keys. To avoid
denial of service attacks, this setting and default was backported to Go
1.19.13, Go 1.20.8, and Go 1.21.1.

Go 1.22 made it an error for a request or response read by a net/http
client or server to have an empty Content-Length header.
This behavior is controlled by the httplaxcontentlength setting.

Go 1.22 changed the behavior of ServeMux to accept extended
patterns and unescape both patterns and request paths by segment.
This behavior can be controlled by the
httpmuxgo121 setting.

Go 1.22 added the Alias type to go/types
for the explicit representation of type aliases.
Whether the type checker produces Alias types or not is controlled by the
gotypesalias setting.
For Go 1.22 it defaults to gotypesalias=0.
For Go 1.23, gotypesalias=1 will become the default.
This setting will be removed in Go 1.27.

Go 1.22 changed the default minimum TLS version supported by both servers
and clients to TLS 1.2. The default can be reverted to TLS 1.0 using the
tls10server setting.
This setting will be removed in Go 1.27.

Go 1.22 changed the default TLS cipher suites used by clients and servers when
not explicitly configured, removing the cipher suites which used RSA based key
exchange. The default can be reverted using the tlsrsakex setting.
This setting will be removed in Go 1.27.

Go 1.22 disabled
ConnectionState.ExportKeyingMaterial
when the connection supports neither TLS 1.3 nor Extended Master Secret
(implemented in Go 1.21). It can be reenabled with the tlsunsafeekm
setting.
This setting will be removed in Go 1.27.

Go 1.22 changed how the runtime interacts with transparent huge pages on Linux.
In particular, a common default Linux kernel configuration can result in
significant memory overheads, and Go 1.22 no longer works around this default.
To work around this issue without adjusting kernel settings, transparent huge
pages can be disabled for Go memory with the
disablethp setting.
This behavior was backported to Go 1.21.1, but the setting is only available
starting with Go 1.21.6.
This setting may be removed in a future release, and users impacted by this issue
should adjust their Linux configuration according to the recommendations in the
GC guide, or switch to a Linux
distribution that disables transparent huge pages altogether.

Go 1.22 added contention on runtime-internal locks to the mutex
profile. Contention on these locks is always
reported at runtime._LostContendedRuntimeLock. Complete stack traces of
runtime locks can be enabled with the runtimecontentionstacks
setting. These stack traces have
non-standard semantics, see setting documentation for details.

Go 1.22 added a new crypto/x509.Certificate
field, Policies, which supports
certificate policy OIDs with components larger than 31 bits. By default this
field is only used during parsing, when it is populated with policy OIDs, but
not used during marshaling. It can be used to marshal these larger OIDs, instead
of the existing PolicyIdentifiers field, by using the
x509usepolicies setting.

Go 1.21 Copy Section

Go 1.21 made it a run-time error to call panic with a nil interface value,
controlled by the panicnil setting.

Go 1.21 made it an error for html/template actions to appear inside of an ECMAScript 6
template literal, controlled by the
jstmpllitinterp setting.
This behavior was backported to Go 1.19.8+ and Go 1.20.3+.

Go 1.21 introduced a limit on the maximum number of MIME headers and multipart
forms, controlled by the
multipartmaxheaders and multipartmaxparts settings
respectively.
This behavior was backported to Go 1.19.8+ and Go 1.20.3+.

Go 1.21 adds the support of Multipath TCP but it is only used if the application
explicitly asked for it. This behavior can be controlled by the
multipathtcp setting.

There is no plan to remove any of these settings.

Go 1.20 Copy Section

Go 1.20 introduced support for rejecting insecure paths in tar and zip archives,
controlled by the tarinsecurepath setting
and the zipinsecurepath setting.
These default to tarinsecurepath=1 and zipinsecurepath=1,
preserving the behavior of earlier versions of Go.
A future version of Go may change the defaults to
tarinsecurepath=0 and zipinsecurepath=0.

Go 1.20 introduced automatic seeding of the
math/rand global random number generator,
controlled by the randautoseed setting.

Go 1.20 introduced the concept of fallback roots for use during certificate verification,
controlled by the x509usefallbackroots setting.

Go 1.20 removed the preinstalled .a files for the standard library
from the Go distribution.
Installations now build and cache the standard library like
packages in other modules.
The installgoroot setting
restores the installation and use of preinstalled .a files.

There is no plan to remove any of these settings.

Go 1.19 Copy Section

Go 1.19 made it an error for path lookups to resolve to binaries in the current directory,
controlled by the execerrdot setting.
There is no plan to remove this setting.

Go 1.19 started sending EDNS0 additional headers on DNS requests.
This can reportedly break the DNS server provided on some routers,
such as CenturyLink Zyxel C3000Z.
This can be changed by the netedns0 setting.
This setting is available in Go 1.21.12, Go 1.22.5, Go 1.23, and later.
There is no plan to remove this setting.

Go 1.18 Copy Section

Go 1.18 removed support for SHA1 in most X.509 certificates,
controlled by the x509sha1 setting.
This setting was removed in Go 1.24.

Go 1.10 Copy Section

Go 1.10 changed how build caching worked and added test caching, along
with the gocacheverify, gocachehash, and gocachetest settings.
There is no plan to remove these settings.

Go 1.6 Copy Section

Go 1.6 introduced transparent support for HTTP/2,
controlled by the http2client, http2server, and http2debug settings.
There is no plan to remove these settings.

Go 1.5 Copy Section

Go 1.5 introduced a pure Go DNS resolver,
controlled by the netdns setting.
There is no plan to remove this setting.

Doc Next 3 Tools (`doc/next/3-tools.md`) Copy Section

Tools {#tools} Copy Chapter

Go command {#go-command} Copy Section

Cgo {#cgo} Copy Section

Vet {#vet} Copy Section

The new scannererr
analyzer checks for failure to handle scanner errors after a loop
around [bufio.Scanner.Scan], which may cause scanning or I/O errors to
go unreported.

The sqlrowserr
analyzer performs a similar check for loops around [sql.Rows.Next],
so that iteration errors are correctly distinguished from a smaller result.

Doc Next 5 Toolchain (`doc/next/5-toolchain.md`) Copy Section

Compiler {#compiler} Copy Chapter

Assembler {#assembler} Copy Chapter

Linker {#linker} Copy Chapter

Bootstrap {#boostrap} Copy Chapter

As mentioned in the Go 1.26 release notes, Go 1.28 now requires
Go 1.26.0 or later for bootstrap.
We expect that Go 1.30 will require a minor release of Go 1.28.0 or later for bootstrap.

Src Go Doc Testdata Template (`src/go/doc/testdata/template.txt`) Copy Section

{{synopsis .Doc}}
PACKAGE {{.Name}}

IMPORTPATH
{{.ImportPath}}

{{with .Imports}}IMPORTS
{{range .}} {{.}}
{{end}}
{{end}}{{/*

/}}FILENAMES
{{range .Filenames}} {{.}}
{{end}}{{/

*/}}{{with .Consts}}
CONSTANTS
{{range .}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{end}}{{/*

*/}}{{with .Vars}}
VARIABLES
{{range .}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{end}}{{/*

*/}}{{with .Funcs}}
FUNCTIONS
{{range .}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{end}}{{/*

*/}}{{with .Types}}
TYPES
{{range .}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{range .Consts}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{/*

*/}}{{range .Vars}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{/*

*/}}{{range .Funcs}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{/*

*/}}{{range .Methods}} {{synopsis .Doc}}
{{node .Decl $.FSet}}

{{end}}{{end}}{{end}}{{/*

*/}}{{with .Bugs}}
BUGS .Bugs is now deprecated, please use .Notes instead
{{range .}}{{indent "\t" .}}
{{end}}{{end}}{{with .Notes}}{{range $marker, $content := .}}
{{$marker}}S
{{range $content}}{{$marker}}({{.UID}}){{indent "\t" .Body}}
{{end}}{{end}}{{end}}

Doc Next 6 Stdlib 99 Minor Embed 80822 (`doc/next/6-stdlib/99-minor/embed/80822.md`) Copy Section

The ReadAt methods of files returned by [embed.FS] now return
[io.EOF] when called with an offset at or beyond the end of the
file, as required by [io.ReaderAt].

Doc Next 6 Stdlib 99 Minor Flag 65675 (`doc/next/6-stdlib/99-minor/flag/65675.md`) Copy Section

The new [FlagSet.All] method returns an iterator over all the flags in the FlagSet;
the function [All] does the same for the global [CommandLine] flag set.
The new [Flag.IsSet] field indicates whether the flag has been set.

Doc Next 6 Stdlib 99 Minor Net 29678 (`doc/next/6-stdlib/99-minor/net/29678.md`) Copy Section

The [IPMask], [IPNet], and [HardwareAddr] types each now implement
a [encoding.TextUnmarshaler] method. This method will recognize
the current marshaling of those types, as well as a planned future
marshaling format. The future marshaling format will be readable
in JSON format, unlike the current format which is a base64 encoding.
The future marshaling format will become the default in a later Go release.
This is being done as a two-step process so that JSON generated
by this release of Go can still be read by earlier releases of Go.

Doc Next 6 Stdlib 99 Minor Regexp 61902 (`doc/next/6-stdlib/99-minor/regexp/61902.md`) Copy Section

New [Regexp.All], [Regexp.AllIndex], [Regexp.AllString], [Regexp.AllStringIndex],
[Regexp.AllStringIndex], [Regexp.AllStringSubmatchIndex], [Regexp.AllSubmatch], and
[Regexp.AllSubmatchIndex] iterator methods on [Regexp] allow incremental matching of the input.

The new [Regexp.SplitSeq] method iterates over the results of splitting the input with the
regular expression.

Doc Next 6 Stdlib 99 Minor Syscall 68595 (`doc/next/6-stdlib/99-minor/syscall/68595.md`) Copy Section

On Linux, [SysProcAttr] now supports enforcement of Landlock policies
and the PR_SET_NO_NEW_PRIVS flag for newly spawned subprocesses.

Doc Next 6 Stdlib 99 Minor Time 67066 (`doc/next/6-stdlib/99-minor/time/67066.md`) Copy Section

On Windows, the monotonic clock used by [Now] now has a resolution of
100 nanoseconds. Previously, its resolution was on the order of milliseconds.
This improves the precision of elapsed-time measurements, such as those
made with [Since].

Src Go Doc Comment Testdata Blank (`src/go/doc/comment/testdata/blank.txt`) Copy Section

-- input --
$
Blank line at start and end.
$
-- gofmt --
Blank line at start and end.
-- text --
Blank line at start and end.
-- markdown --
Blank line at start and end.
-- html --
Blank line at start and end.

Src Go Doc Comment Testdata Code (`src/go/doc/comment/testdata/code.txt`) Copy Section

-- input --
Text.
A tab-indented
(no, not eight-space indented)
code block and haiku.
More text.
One space
is
enough
to
start
a
block.
More text.

Blocks
can

have
blank
lines.
-- gofmt --
Text.

A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.

One space
 is
  enough
   to
    start
     a
      block.

More text.

Blocks
  can

have
  blank
    lines.

-- markdown --
Text.

A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.

One space
 is
  enough
   to
    start
     a
      block.

More text.

Blocks
  can

have
  blank
    lines.

-- html --
Text.
A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.
One space
is
enough
to
start
a
block.

More text.
Blocks
can

have
blank
lines.

Src Go Doc Comment Testdata Code2 (`src/go/doc/comment/testdata/code2.txt`) Copy Section

-- input --
Text.

A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.
-- gofmt --
Text.

A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.
-- markdown --
Text.

A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.
-- html --
Text.
A tab-indented
(no, not eight-space indented)
code block and haiku.

More text.

Src Go Doc Comment Testdata Code3 (`src/go/doc/comment/testdata/code3.txt`) Copy Section

-- input --
Text.

$
A tab-indented
(surrounded by more blank lines)
code block and haiku.
$

More text.
-- gofmt --
Text.

A tab-indented
(surrounded by more blank lines)
code block and haiku.

More text.
-- markdown --
Text.

A tab-indented
(surrounded by more blank lines)
code block and haiku.

More text.
-- html --
Text.
A tab-indented
(surrounded by more blank lines)
code block and haiku.

More text.

Src Go Doc Comment Testdata Code4 (`src/go/doc/comment/testdata/code4.txt`) Copy Section

-- input --
To test, run this command:
go test -more

Or, to test specific things, run this command:

go test -more
-pkg first/package
-pkg second/package
-pkg third/package

Happy testing!
-- gofmt --
To test, run this command:

go test -more

Or, to test specific things, run this command:

go test -more \
  -pkg first/package \
  -pkg second/package \
  -pkg third/package

Happy testing!
-- markdown --
To test, run this command:

go test -more

Or, to test specific things, run this command:

go test -more \
  -pkg first/package \
  -pkg second/package \
  -pkg third/package

Happy testing!

Src Go Doc Comment Testdata Code5 (`src/go/doc/comment/testdata/code5.txt`) Copy Section

-- input --
L1
L2
L3
L4
L5

• L6 {
  L7
  }
  L8
  -- gofmt --
  L1
  L2
  L3
  L4
  L5
  • L6 {
    L7
    }

L8

Src Go Doc Comment Testdata Code6 (`src/go/doc/comment/testdata/code6.txt`) Copy Section

-- input --
Run this program:

func main() {
fmt.Println("hello, world")
}

Or this:

go func() {
fmt.Println("hello, world")
}()
-- gofmt --
Run this program:

func main() {
	fmt.Println("hello, world")
}

Or this:

go func() {
	fmt.Println("hello, world")
}()

Src Go Doc Comment Testdata Crash1 (`src/go/doc/comment/testdata/crash1.txt`) Copy Section

-- input --
[]

[]: http://
-- gofmt --
[]

[]: http://
-- html --

-- markdown --

-- text --

[]: http://

Src Go Doc Comment Testdata Doclink (`src/go/doc/comment/testdata/doclink.txt`) Copy Section

-- input --
In this package, see [Doc] and [Parser.Parse].
There is no [Undef] or [Undef.Method].
See also the [comment] package,
especially [comment.Doc] and [comment.Parser.Parse].
-- gofmt --
In this package, see [Doc] and [Parser.Parse].
There is no [Undef] or [Undef.Method].
See also the [comment] package,
especially [comment.Doc] and [comment.Parser.Parse].
-- text --
In this package, see Doc and Parser.Parse. There is no [Undef] or
[Undef.Method]. See also the comment package, especially comment.Doc and
comment.Parser.Parse.
-- markdown --
In this package, see Doc and Parser.Parse. There is no [Undef] or [Undef.Method]. See also the comment package, especially comment.Doc and comment.Parser.Parse.
-- html --
In this package, see Doc and Parser.Parse.
There is no [Undef] or [Undef.Method].
See also the comment package,
especially comment.Doc and comment.Parser.Parse.

Src Go Doc Comment Testdata Doclink2 (`src/go/doc/comment/testdata/doclink2.txt`) Copy Section

-- input --
We use [io.Reader] a lot, and also a few map[io.Reader]string.

Never [io.Reader]int or Slice[io.Reader] though.
-- markdown --
We use io.Reader a lot, and also a few map[io.Reader]string.

Never [io.Reader]int or Slice[io.Reader] though.

Src Go Doc Comment Testdata Doclink3 (`src/go/doc/comment/testdata/doclink3.txt`) Copy Section

-- input --
[encoding/json.Marshal] is a doc link.

[rot13.Marshal] is not.
-- markdown --
encoding/json.Marshal is a doc link.

[rot13.Marshal] is not.

Src Go Doc Comment Testdata Doclink4 (`src/go/doc/comment/testdata/doclink4.txt`) Copy Section

-- input --
[io] at start of comment.
[io] at start of line.
At end of line: [io]
At end of comment: [io]
-- markdown --
io at start of comment. io at start of line. At end of line: io At end of comment: io

Src Go Doc Comment Testdata Doclink5 (`src/go/doc/comment/testdata/doclink5.txt`) Copy Section

{"DocLinkBaseURL": "https://pkg.go.dev"}
-- input --
[encoding/json.Marshal] is a doc link.
-- markdown --
encoding/json.Marshal is a doc link.

Src Go Doc Comment Testdata Doclink6 (`src/go/doc/comment/testdata/doclink6.txt`) Copy Section

{"DocLinkBaseURL": "https://go.dev/pkg/"}
-- input --
[encoding/json.Marshal] is a doc link, and so is [rsc.io/quote.NonExist].
-- markdown --
encoding/json.Marshal is a doc link, and so is rsc.io/quote.NonExist.

Src Go Doc Comment Testdata Doclink7 (`src/go/doc/comment/testdata/doclink7.txt`) Copy Section

-- input --
You see more [*bytes.Buffer] than [bytes.Buffer].
-- markdown --
You see more *bytes.Buffer than bytes.Buffer.

Src Go Doc Comment Testdata Escape (`src/go/doc/comment/testdata/escape.txt`) Copy Section

-- input --
What the ~!@#$%^&*()_+-=`{}|[]:";',./<>?

• Line

• Line

• Line

999. Line

Line Copy Chapter

-- gofmt --
What the ~!@#$%^&*()_+-=`{}|[]:";',./<>?

• Line

• Line

• Line

999. Line

Line Copy Chapter

-- text --
What the ~!@#$%^&*()_+-=`{}|[]:";',./<>?

• Line

• Line

• Line

999. Line

Line Copy Chapter

-- markdown --
What the ~!@#$%^&*()_+-=`{}|[]\:";',./<>?

+ Line

- Line

* Line

999. Line

## Line
-- html --
What the ~!@#$%^&*()_+-=`{}|[]:";',./<>?

• Line

• Line

• Line

999. Line

Line Copy Chapter

Src Go Doc Comment Testdata Head (`src/go/doc/comment/testdata/head.txt`) Copy Section

-- input --
Some text.

An Old Heading

Not An Old Heading.

And some text.

A New Heading.

And some more text.

Not a heading,

because text follows it.

Because text precedes it,

not a heading.

Not a heading either. Copy Chapter

-- gofmt --
Some text.

An Old Heading

Not An Old Heading.

And some text.

A New Heading.

And some more text.

Not a heading,

because text follows it.

Because text precedes it,

not a heading.

Not a heading either. Copy Chapter

-- text --
Some text.

An Old Heading

Not An Old Heading.

And some text.

A New Heading.

And some more text.

Not a heading, because text follows it.

Because text precedes it, # not a heading.

Not a heading either. Copy Chapter

-- markdown --
Some text.

An Old Heading {#hdr-An_Old_Heading} Copy Section

Not An Old Heading.

And some text.

A New Heading. {#hdr-A_New_Heading_} Copy Section

And some more text.

# Not a heading, because text follows it.

Because text precedes it, # not a heading.

## Not a heading either.

-- html --
Some text.

An Old Heading

A New Heading.

Src Go Doc Comment Testdata Head2 (`src/go/doc/comment/testdata/head2.txt`) Copy Section

-- input --
✦

Almost a+heading

✦

Don't be a heading

✦

A.b is a heading

✦

A. b is not a heading

✦
-- gofmt --
✦

Almost a+heading

✦

Don't be a heading

✦

A.b is a heading

✦

A. b is not a heading

✦

Src Go Doc Comment Testdata Head3 (`src/go/doc/comment/testdata/head3.txt`) Copy Section

{"HeadingLevel": 5}
-- input --

Heading

-- markdown --

Heading {#hdr-Heading}

-- html --

Heading

Src Go Doc Comment Testdata Hello (`src/go/doc/comment/testdata/hello.txt`) Copy Section

-- input --
Hello,
world

This is
a test.

-- dump --
Doc
Paragraph
Plain
"Hello,\n"
"world"
Paragraph
Plain
"This is\n"
"a test."
-- gofmt --
Hello,
world

This is
a test.
-- html --
Hello,
world
This is
a test.
-- markdown --
Hello, world

This is a test.
-- text --
Hello, world

This is a test.

Src Go Doc Comment Testdata Link (`src/go/doc/comment/testdata/link.txt`) Copy Section

-- input --
The Go home page is https://go.dev/.
It used to be https://golang.org.

-- gofmt --
The Go home page is https://go.dev/.
It used to be https://golang.org.

-- text --
The Go home page is https://go.dev/. It used to be https://golang.org.

-- markdown --
The Go home page is https://go.dev/. It used to be https://golang.org.

-- html --
The Go home page is https://go.dev/.
It used to be https://golang.org.

Src Go Doc Comment Testdata Link2 (`src/go/doc/comment/testdata/link2.txt`) Copy Section

-- input --
The Go home page is https://go.dev/.
It used to be https://golang.org.
https:// is not a link.
Nor is https://
https://☺ is not a link.
https://:80 is not a link.

-- gofmt --
The Go home page is https://go.dev/.
It used to be https://golang.org.
https:// is not a link.
Nor is https://
https://☺ is not a link.
https://:80 is not a link.

-- text --
The Go home page is https://go.dev/. It used to be https://golang.org. https://
is not a link. Nor is https:// https://☺ is not a link. https://:80 is not a
link.

-- markdown --
The Go home page is https://go.dev/. It used to be https://golang.org. https:// is not a link. Nor is https:// https://☺ is not a link. https://:80 is not a link.

-- html --
The Go home page is https://go.dev/.
It used to be https://golang.org.
https:// is not a link.
Nor is https://
https://☺ is not a link.
https://:80 is not a link.

Src Go Doc Comment Testdata Link3 (`src/go/doc/comment/testdata/link3.txt`) Copy Section

-- input --
Doc text.

-- gofmt --
Doc text.

-- text --
Doc text.
-- markdown --
Doc text.
-- html --
Doc text.

Src Go Doc Comment Testdata Link4 (`src/go/doc/comment/testdata/link4.txt`) Copy Section

-- input --
These are not links.

[x

x:

xhttps://go.dev

But this is, with a tab (although it's unused).

z: https://go.dev
-- gofmt --
These are not links.

[x

x:

xhttps://go.dev

But this is, with a tab (although it's unused).

-- text --
These are not links.

[x

x:

xhttps://go.dev

But this is, with a tab (although it's unused).
-- markdown --
These are not links.

[x

[x]:

[x]:https://go.dev

[x]https://go.dev

[x]: surprise://go.dev

[x]: surprise!

But this is, with a tab (although it's unused).
-- html --
These are not links.
[x
x:
x:https://go.dev
[x]https://go.dev
x: surprise://go.dev
x: surprise!
But this is, with a tab (although it's unused).

Src Go Doc Comment Testdata Link5 (`src/go/doc/comment/testdata/link5.txt`) Copy Section

-- input --
See the Go home page and the pkg
site.

They're really great!

-- gofmt --
See the Go home page and the pkg
site.

They're really great!

-- text --
See the Go home page and the pkg site.

They're really great!

-- markdown --
See the Go home page and the pkg site.

They're really great!
-- html --
See the Go home page and the pkg
site.
They're really great!

Src Go Doc Comment Testdata Link6 (`src/go/doc/comment/testdata/link6.txt`) Copy Section

-- input --
URLs with punctuation are hard.
We don't want to consume the end-of-sentence punctuation.

For example, https://en.wikipedia.org/wiki/John_Adams_(miniseries).
And https://example.com/[foo]/bar{.
And https://example.com/(foo)/bar!
And https://example.com/{foo}/bar{.
And https://example.com/)baz{foo}.

[And https://example.com/].

-- gofmt --
URLs with punctuation are hard.
We don't want to consume the end-of-sentence punctuation.

For example, https://en.wikipedia.org/wiki/John_Adams_(miniseries).
And https://example.com/[foo]/bar{.
And https://example.com/(foo)/bar!
And https://example.com/{foo}/bar{.
And https://example.com/)baz{foo}.

[And https://example.com/].

-- text --
URLs with punctuation are hard. We don't want to consume the end-of-sentence
punctuation.

For example, https://en.wikipedia.org/wiki/John_Adams_(miniseries).
And https://example.com/[foo]/bar{. And https://example.com/(foo)/bar! And
https://example.com/{foo}/bar{. And https://example.com/)baz{foo}.

[And https://example.com/].

-- markdown --
URLs with punctuation are hard. We don't want to consume the end-of-sentence punctuation.

For example, https://en.wikipedia.org/wiki/John_Adams_(miniseries). And [https://example.com/\[foo]/bar](https://example.com/[foo]/bar){. And https://example.com/(foo)/bar! And https://example.com/{foo}/bar{. And https://example.com/)baz{foo}.

[And https://example.com/].

-- html --
URLs with punctuation are hard.
We don't want to consume the end-of-sentence punctuation.
For example, https://en.wikipedia.org/wiki/John_Adams_(miniseries).
And https://example.com/[foo]/bar{.
And https://example.com/(foo)/bar!
And https://example.com/{foo}/bar{.
And https://example.com/)baz{foo}.
[And https://example.com/].

Src Go Doc Comment Testdata Link7 (`src/go/doc/comment/testdata/link7.txt`) Copy Section

-- input --
math is a package but this is not a doc link.

[io] is a doc link.

-- gofmt --
math is a package but this is not a doc link.

[io] is a doc link.

-- text --
math is a package but this is not a doc link.

io is a doc link.

-- markdown --
math is a package but this is not a doc link.

io is a doc link.
-- html --
math is a package but this is not a doc link.
io is a doc link.

Src Go Doc Comment Testdata Linklist (`src/go/doc/comment/testdata/linklist.txt`) Copy Section

{"DocLinkBaseURL": "https://pkg.go.dev"}
-- input --
Did you know?

• [encoding/json.Marshal] is a doc link. So is [encoding/json.Unmarshal].
  -- text --
  Did you know?

• encoding/json.Marshal is a doc link. So is encoding/json.Unmarshal.
  -- markdown --
  Did you know?

• encoding/json.Marshal is a doc link. So is encoding/json.Unmarshal.
  -- html --
  Did you know?

1. This list
2. Starts the comment
3. And also has a blank line before it.

-

- $

- $

1! List.

-

-

-

1! List.

-

- $

- $

1! List.

Code block here.

The implementation compiles a custom codec for each data
                type in the stream and is most efficient when a single
                Encoder is used to transmit a stream of values, amortizing
                the cost of compilation.

Code block here.