The latest Go release, version 1.18, is a significant release, including changes to the language, implementation of the toolchain, runtime, and libraries. Go 1.18 arrives seven months after Go 1.17. As always, the release maintains the Go 1 promise of compatibility. We expect almost all Go programs to continue to compile and run as before.
Go 1.18 includes an implementation of generic features as described by the Type Parameters Proposal. This includes major - but fully backward-compatible - changes to the language.
These new language changes required a large amount of new code that has not had significant testing in production settings. That will only happen as more people write and use generic code. We believe that this feature is well implemented and high quality. However, unlike most aspects of Go, we can't back up that belief with real world experience. Therefore, while we encourage the use of generics where it makes sense, please use appropriate caution when deploying generic code in production.
While we believe that the new language features are well designed and clearly specified, it is possible that we have made mistakes. We want to stress that the Go 1 compatibility guarantee says “If it becomes necessary to address an inconsistency or incompleteness in the specification, resolving the issue could affect the meaning or legality of existing programs. We reserve the right to address such issues, including updating the implementations.” It also says “If a compiler or library has a bug that violates the specification, a program that depends on the buggy behavior may break if the bug is fixed. We reserve the right to fix such bugs.” In other words, it is possible that there will be code using generics that will work with the 1.18 release but break in later releases. We do not plan or expect to make any such change. However, breaking 1.18 programs in future releases may become necessary for reasons that we cannot today foresee. We will minimize any such breakage as much as possible, but we can't guarantee that the breakage will be zero.
The following is a list of the most visible changes. For a more comprehensive overview, see the proposal. For details see the language spec.
~
has been added to the set of operators and punctuation.~T
type elements. Such interfaces may only be used as type constraints. An interface now defines a set of types as well as a set of methods.any
is an alias for the empty interface. It may be used instead of interface{}
.comparable
is an interface that denotes the set of all types which can be compared using ==
or !=
. It may only be used as (or embedded in) a type constraint.There are three experimental packages using generics that may be useful. These packages are in x/exp repository; their API is not covered by the Go 1 guarantee and may change as we gain more experience with generics.
golang.org/x/exp/constraints
Constraints that are useful for generic code, such as constraints.Ordered
.
golang.org/x/exp/slices
A collection of generic functions that operate on slices of any element type.
golang.org/x/exp/maps
A collection of generic functions that operate on maps of any key or element type.
The current generics implementation has the following known limitations:
real
, imag
, and complex
. We hope to remove this restriction in a future release.m
on a value x
of type parameter type P
if m
is explicitly declared by P
's constraint interface. Similarly, method values x.m
and method expressions P.m
also are only supported if m
is explicitly declared by P
, even though m
might be in the method set of P
by virtue of the fact that all types in P
implement m
. We hope to remove this restriction in a future release.x.f
where x
is of type parameter type even if all types in the type parameter's type set have a field f
. We may remove this restriction in a future release.Generics also represent a large change for the Go ecosystem. While we have updated several core tools with generics support, there is much more to do. It will take time for remaining tools, documentation, and libraries to catch up with these language changes.
The Go 1.18 compiler now correctly reports declared but not used
errors for variables that are set inside a function literal but are never used. Before Go 1.18, the compiler did not report an error in such cases. This fixes long-outstanding compiler issue #8560. As a result of this change, (possibly incorrect) programs may not compile anymore. The necessary fix is straightforward: fix the program if it was in fact incorrect, or use the offending variable, for instance by assigning it to the blank identifier _
. Since go vet
always pointed out this error, the number of affected programs is likely very small.
The Go 1.18 compiler now reports an overflow when passing a rune constant expression such as '1' << 32
as an argument to the predeclared functions print
and println
, consistent with the behavior of user-defined functions. Before Go 1.18, the compiler did not report an error in such cases but silently accepted such constant arguments if they fit into an int64
. As a result of this change, (possibly incorrect) programs may not compile anymore. The necessary fix is straightforward: fix the program if it was in fact incorrect, or explicitly convert the offending argument to the correct type. Since go vet
always pointed out this error, the number of affected programs is likely very small.
Go 1.18 introduces the new GOAMD64
environment variable, which selects at compile time a minimum target version of the AMD64 architecture. Allowed values are v1
, v2
, v3
, or v4
. Each higher level requires, and takes advantage of, additional processor features. A detailed description can be found here.
The GOAMD64
environment variable defaults to v1
.
The 64-bit RISC-V architecture on Linux (the linux/riscv64
port) now supports the c-archive
and c-shared
build modes.
Go 1.18 requires Linux kernel version 2.6.32 or later.
The windows/arm
and windows/arm64
ports now support non-cooperative preemption, bringing that capability to all four Windows ports, which should hopefully address subtle bugs encountered when calling into Win32 functions that block for extended periods of time.
On iOS (the ios/arm64
port) and iOS simulator running on AMD64-based macOS (the ios/amd64
port), Go 1.18 now requires iOS 12 or later; support for previous versions has been discontinued.
Go 1.18 is the last release that is supported on FreeBSD 11.x, which has already reached end-of-life. Go 1.19 will require FreeBSD 12.2+ or FreeBSD 13.0+. FreeBSD 13.0+ will require a kernel with the COMPAT_FREEBSD12 option set (this is the default).
Go 1.18 includes an implementation of fuzzing as described by the fuzzing proposal.
See the fuzzing landing page to get started.
Please be aware that fuzzing can consume a lot of memory and may impact your machine’s performance while it runs. Also be aware that the fuzzing engine writes values that expand test coverage to a fuzz cache directory within $GOCACHE/fuzz
while it runs. There is currently no limit to the number of files or total bytes that may be written to the fuzz cache, so it may occupy a large amount of storage (possibly several GBs).
go
get
go
get
no longer builds or installs packages in module-aware mode. go
get
is now dedicated to adjusting dependencies in go.mod
. Effectively, the -d
flag is always enabled. To install the latest version of an executable outside the context of the current module, use go
install
example.com/cmd@latest
. Any version query may be used instead of latest
. This form of go
install
was added in Go 1.16, so projects supporting older versions may need to provide install instructions for both go
install
and go
get
. go
get
now reports an error when used outside a module, since there is no go.mod
file to update. In GOPATH mode (with GO111MODULE=off
), go
get
still builds and installs packages, as before.
go.mod
and go.sum
updatesThe go
mod
graph
, go
mod
vendor
, go
mod
verify
, and go
mod
why
subcommands no longer automatically update the go.mod
and go.sum
files. (Those files can be updated explicitly using go
get
, go
mod
tidy
, or go
mod
download
.)
go
version
The go
command now embeds version control information in binaries. It includes the currently checked-out revision, commit time, and a flag indicating whether edited or untracked files are present. Version control information is embedded if the go
command is invoked in a directory within a Git, Mercurial, Fossil, or Bazaar repository, and the main
package and its containing main module are in the same repository. This information may be omitted using the flag -buildvcs=false
.
Additionally, the go
command embeds information about the build, including build and tool tags (set with -tags
), compiler, assembler, and linker flags (like -gcflags
), whether cgo was enabled, and if it was, the values of the cgo environment variables (like CGO_CFLAGS
). Both VCS and build information may be read together with module information using go
version
-m
file
or runtime/debug.ReadBuildInfo
(for the currently running binary) or the new debug/buildinfo
package.
The underlying data format of the embedded build information can change with new go releases, so an older version of go
may not handle the build information produced with a newer version of go
. To read the version information from a binary built with go
1.18, use the go
version
command and the debug/buildinfo
package from go
1.18+.
go
mod
download
If the main module‘s go.mod
file specifies go
1.17
or higher, go
mod
download
without arguments now downloads source code for only the modules explicitly required in the main module’s go.mod
file. (In a go
1.17
or higher module, that set already includes all dependencies needed to build the packages and tests in the main module.) To also download source code for transitive dependencies, use go
mod
download
all
.
go
mod
vendor
The go
mod
vendor
subcommand now supports a -o
flag to set the output directory. (Other go
commands still read from the vendor
directory at the module root when loading packages with -mod=vendor
, so the main use for this flag is for third-party tools that need to collect package source code.)
go
mod
tidy
The go
mod
tidy
command now retains additional checksums in the go.sum
file for modules whose source code is needed to verify that each imported package is provided by only one module in the build list. Because this condition is rare and failure to apply it results in a build error, this change is not conditioned on the go
version in the main module's go.mod
file.
go
work
The go
command now supports a “Workspace” mode. If a go.work
file is found in the working directory or a parent directory, or one is specified using the GOWORK
environment variable, it will put the go
command into workspace mode. In workspace mode, the go.work
file will be used to determine the set of main modules used as the roots for module resolution, instead of using the normally-found go.mod
file to specify the single main module. For more information see the go work
documentation.
go
build
-asan
The go
build
command and related commands now support an -asan
flag that enables interoperation with C (or C++) code compiled with the address sanitizer (C compiler option -fsanitize=address
).
go
test
The go
command now supports additional command line options for the new fuzzing support described above:
go test
supports -fuzz
, -fuzztime
, and -fuzzminimizetime
options. For documentation on these see go help testflag
.go clean
supports a -fuzzcache
option. For documentation see go help clean
.//go:build
linesGo 1.17 introduced //go:build
lines as a more readable way to write build constraints, instead of //
+build
lines. As of Go 1.17, gofmt
adds //go:build
lines to match existing +build
lines and keeps them in sync, while go
vet
diagnoses when they are out of sync.
Since the release of Go 1.18 marks the end of support for Go 1.16, all supported versions of Go now understand //go:build
lines. In Go 1.18, go
fix
now removes the now-obsolete //
+build
lines in modules declaring go
1.18
or later in their go.mod
files.
For more information, see https://go.dev/design/draft-gobuild.
gofmt
now reads and formats input files concurrently, with a memory limit proportional to GOMAXPROCS
. On a machine with multiple CPUs, gofmt
should now be significantly faster.
The vet
tool is updated to support generic code. In most cases, it reports an error in generic code whenever it would report an error in the equivalent non-generic code after substituting for type parameters with a type from their type set. For example, vet
reports a format error in
func Print[T ~int|~string](t T) { fmt.Printf("%d", t) }
because it would report a format error in the non-generic equivalent of Print[string]
:
func PrintString(x string) { fmt.Printf("%d", x) }
The cmd/vet
checkers copylock
, printf
, sortslice
, testinggoroutine
, and tests
have all had moderate precision improvements to handle additional code patterns. This may lead to newly reported errors in existing packages. For example, the printf
checker now tracks formatting strings created by concatenating string constants. So vet
will report an error in:
// fmt.Printf formatting directive %d is being passed to Println. fmt.Println("%d"+` ≡ x (mod 2)`+"\n", x%2)
The garbage collector now includes non-heap sources of garbage collector work (e.g., stack scanning) when determining how frequently to run. As a result, garbage collector overhead is more predictable when these sources are significant. For most applications these changes will be negligible; however, some Go applications may now use less memory and spend more time on garbage collection, or vice versa, than before. The intended workaround is to tweak GOGC
where necessary.
The runtime now returns memory to the operating system more efficiently and has been tuned to work more aggressively as a result.
Go 1.17 generally improved the formatting of arguments in stack traces, but could print inaccurate values for arguments passed in registers. This is improved in Go 1.18 by printing a question mark (?
) after each value that may be inaccurate.
The built-in function append
now uses a slightly different formula when deciding how much to grow a slice when it must allocate a new underlying array. The new formula is less prone to sudden transitions in allocation behavior.
Go 1.17 implemented a new way of passing function arguments and results using registers instead of the stack on 64-bit x86 architecture on selected operating systems. Go 1.18 expands the supported platforms to include 64-bit ARM (GOARCH=arm64
), big- and little-endian 64-bit PowerPC (GOARCH=ppc64
, ppc64le
), as well as 64-bit x86 architecture (GOARCH=amd64
) on all operating systems. On 64-bit ARM and 64-bit PowerPC systems, benchmarking shows typical performance improvements of 10% or more.
As mentioned in the Go 1.17 release notes, this change does not affect the functionality of any safe Go code and is designed to have no impact on most assembly code. See the Go 1.17 release notes for more details.
The compiler now can inline functions that contain range loops or labeled for loops.
The new -asan
compiler option supports the new go
command -asan
option.
Because the compiler's type checker was replaced in its entirety to support generics, some error messages now may use different wording than before. In some cases, pre-Go 1.18 error messages provided more detail or were phrased in a more helpful way. We intend to address these cases in Go 1.19.
Because of changes in the compiler related to supporting generics, the Go 1.18 compile speed can be roughly 15% slower than the Go 1.17 compile speed. The execution time of the compiled code is not affected. We intend to improve the speed of the compiler in future releases.
The linker emits far fewer relocations. As a result, most codebases will link faster, require less memory to link, and generate smaller binaries. Tools that process Go binaries should use Go 1.18's debug/gosym
package to transparently handle both old and new binaries.
The new -asan
linker option supports the new go
command -asan
option.
When building a Go release from source and GOROOT_BOOTSTRAP
is not set, previous versions of Go looked for a Go 1.4 or later bootstrap toolchain in the directory $HOME/go1.4
(%HOMEDRIVE%%HOMEPATH%\go1.4
on Windows). Go now looks first for $HOME/go1.17
or $HOME/sdk/go1.17
before falling back to $HOME/go1.4
. We intend for Go 1.19 to require Go 1.17 or later for bootstrap, and this change should make the transition smoother. For more details, see go.dev/issue/44505.
debug/buildinfo
package {#debug_buildinfo}The new debug/buildinfo
package provides access to module versions, version control information, and build flags embedded in executable files built by the go
command. The same information is also available via runtime/debug.ReadBuildInfo
for the currently running binary and via go
version
-m
on the command line.
net/netip
packageThe new net/netip
package defines a new IP address type, Addr
. Compared to the existing net.IP
type, the netip.Addr
type takes less memory, is immutable, and is comparable so it supports ==
and can be used as a map key.
In addition to Addr
, the package defines AddrPort
, representing an IP and port, and Prefix
, representing a network CIDR prefix.
The package also defines several functions to create and examine these new types: AddrFrom4
, AddrFrom16
, AddrFromSlice
, AddrPortFrom
, IPv4Unspecified
, IPv6LinkLocalAllNodes
, IPv6Unspecified
, MustParseAddr
, MustParseAddrPort
, MustParsePrefix
, ParseAddr
, ParseAddrPort
, ParsePrefix
, PrefixFrom
.
The net
package includes new methods that parallel existing methods, but return netip.AddrPort
instead of the heavier-weight net.IP
or *net.UDPAddr
types: Resolver.LookupNetIP
, UDPConn.ReadFromUDPAddrPort
, UDPConn.ReadMsgUDPAddrPort
, UDPConn.WriteToUDPAddrPort
, UDPConn.WriteMsgUDPAddrPort
. The new UDPConn
methods support allocation-free I/O.
The net
package also now includes functions and methods to convert between the existing TCPAddr
/UDPAddr
types and netip.AddrPort
: TCPAddrFromAddrPort
, UDPAddrFromAddrPort
, TCPAddr.AddrPort
, UDPAddr.AddrPort
.
If Config.MinVersion
is not set, it now defaults to TLS 1.2 for client connections. Any safely up-to-date server is expected to support TLS 1.2, and browsers have required it since 2020. TLS 1.0 and 1.1 are still supported by setting Config.MinVersion
to VersionTLS10
. The server-side default is unchanged at TLS 1.0.
The default can be temporarily reverted to TLS 1.0 by setting the GODEBUG=tls10default=1
environment variable. This option will be removed in Go 1.19.
crypto/x509
will now reject certificates signed with the SHA-1 hash function. This doesn't apply to self-signed root certificates. Practical attacks against SHA-1 have been demonstrated since 2017 and publicly trusted Certificate Authorities have not issued SHA-1 certificates since 2015.
This can be temporarily reverted by setting the GODEBUG=x509sha1=1
environment variable. This option will be removed in a future release.
As always, there are various minor changes and updates to the library, made with the Go 1 promise of compatibility in mind.
The new Writer.AvailableBuffer
method returns an empty buffer with a possibly non-empty capacity for use with append-like APIs. After appending, the buffer can be provided to a succeeding Write
call and possibly avoid any copying.
The Reader.Reset
and Writer.Reset
methods now use the default buffer size when called on objects with a nil
buffer.
The new Cut
function slices a []byte
around a separator. It can replace and simplify many common uses of Index
, IndexByte
, IndexRune
, and SplitN
.
Trim
, TrimLeft
, and TrimRight
are now allocation free and, especially for small ASCII cutsets, up to 10 times faster.
The Title
function is now deprecated. It doesn't handle Unicode punctuation and language-specific capitalization rules, and is superseded by the golang.org/x/text/cases package.
The P224
, P384
, and P521
curve implementations are now all backed by code generated by the addchain and fiat-crypto projects, the latter of which is based on a formally-verified model of the arithmetic operations. They now use safer complete formulas and internal APIs. P-224 and P-384 are now approximately four times faster. All specific curve implementations are now constant-time.
Operating on invalid curve points (those for which the IsOnCurve
method returns false, and which are never returned by Unmarshal
or a Curve
method operating on a valid point) has always been undefined behavior, can lead to key recovery attacks, and is now unsupported by the new backend. If an invalid point is supplied to a P224
, P384
, or P521
method, that method will now return a random point. The behavior might change to an explicit panic in a future release.
The new Conn.NetConn
method allows access to the underlying net.Conn
.
Certificate.Verify
now uses platform APIs to verify certificate validity on macOS and iOS when it is called with a nil VerifyOpts.Roots
or when using the root pool returned from SystemCertPool
.
SystemCertPool
is now available on Windows.
On Windows, macOS, and iOS, when a CertPool
returned by SystemCertPool
has additional certificates added to it, Certificate.Verify
will do two verifications: one using the platform verifier APIs and the system roots, and one using the Go verifier and the additional roots. Chains returned by the platform verifier APIs will be prioritized.
CertPool.Subjects
is deprecated. On Windows, macOS, and iOS the CertPool
returned by SystemCertPool
will return a pool which does not include system roots in the slice returned by Subjects
, as a static list can't appropriately represent the platform policies and might not be available at all from the platform APIs.
Support for signing certificates using signature algorithms that depend on the MD5 hash (MD5WithRSA
) may be removed in Go 1.19.
The StructField
and BasicType
structs both now have a DataBitOffset
field, which holds the value of the DW_AT_data_bit_offset
attribute if present.
The R_PPC64_RELATIVE
constant has been added.
The File.Symbols method now returns the new exported error value ErrNoSymbols if the file has no symbol section.
A go:embed
directive may now start with all:
to include files whose names start with dot or underscore.
Per the proposal Additions to go/ast and go/token to support parameterized functions and types the following additions are made to the go/ast
package:
FuncType
and TypeSpec
nodes have a new field TypeParams
to hold type parameters, if any.IndexListExpr
represents index expressions with multiple indices, used for function and type instantiations with more than one explicit type argument.The new Kind.String
method returns a human-readable name for the receiver kind.
The new constant TILDE
represents the ~
token per the proposal Additions to go/ast and go/token to support parameterized functions and types .
The new Config.GoVersion
field sets the accepted Go language version.
Per the proposal Additions to go/types to support type parameters the following additions are made to the go/types
package:
TypeParam
, factory function NewTypeParam
, and associated methods are added to represent a type parameter.TypeParamList
holds a list of type parameters.TypeList
holds a list of types.NewSignatureType
allocates a Signature
with (receiver or function) type parameters. To access those type parameters, the Signature
type has two new methods Signature.RecvTypeParams
and Signature.TypeParams
.Named
types have four new methods: Named.Origin
to get the original parameterized types of instantiated types, Named.TypeArgs
and Named.TypeParams
to get the type arguments or type parameters of an instantiated or parameterized type, and Named.SetTypeParams
to set the type parameters (for instance, when importing a named type where allocation of the named type and setting of type parameters cannot be done simultaneously due to possible cycles).Interface
type has four new methods: Interface.IsComparable
and Interface.IsMethodSet
to query properties of the type set defined by the interface, and Interface.MarkImplicit
and Interface.IsImplicit
to set and test whether the interface is an implicit interface around a type constraint literal.Union
and Term
, factory functions NewUnion
and NewTerm
, and associated methods are added to represent type sets in interfaces.Instantiate
instantiates a parameterized type.Info.Instances
map records function and type instantiations through the new Instance
type.ArgumentError
and associated methods are added to represent an error related to a type argument.Context
and factory function NewContext
are added to facilitate sharing of identical type instances across type-checked packages, via the new Config.Context
field.The predicates AssignableTo
, ConvertibleTo
, Implements
, Identical
, IdenticalIgnoreTags
, and AssertableTo
now also work with arguments that are or contain generalized interfaces, i.e. interfaces that may only be used as type constraints in Go code. Note that the behavior of AssignableTo
, ConvertibleTo
, Implements
, and AssertableTo
is undefined with arguments that are uninstantiated generic types, and AssertableTo
is undefined if the first argument is a generalized interface.
Within a range
pipeline the new {{break}}
command will end the loop early and the new {{continue}}
command will immediately start the next loop iteration.
The and
function no longer always evaluates all arguments; it stops evaluating arguments after the first argument that evaluates to false. Similarly, the or
function now stops evaluating arguments after the first argument that evaluates to true. This makes a difference if any of the arguments is a function call.
The Draw
and DrawMask
fallback implementations (used when the arguments are not the most common image types) are now faster when those arguments implement the optional draw.RGBA64Image
and image.RGBA64Image
interfaces that were added in Go 1.17.
net.Error.Temporary
has been deprecated.
On WebAssembly targets, the Dial
, DialContext
, DialTLS
and DialTLSContext
method fields in Transport
will now be correctly used, if specified, for making HTTP requests.
The new Cookie.Valid
method reports whether the cookie is valid.
The new MaxBytesHandler
function creates a Handler
that wraps its ResponseWriter
and Request.Body
with a MaxBytesReader
.
When looking up a domain name containing non-ASCII characters, the Unicode-to-ASCII conversion is now done in accordance with Nontransitional Processing as defined in the Unicode IDNA Compatibility Processing standard (UTS #46). The interpretation of four distinct runes are changed: ß, ς, zero-width joiner U+200D, and zero-width non-joiner U+200C. Nontransitional Processing is consistent with most applications and web browsers.
User.GroupIds
now uses a Go native implementation when cgo is not available.
The new Value.SetIterKey
and Value.SetIterValue
methods set a Value using a map iterator as the source. They are equivalent to Value.Set(iter.Key())
and Value.Set(iter.Value())
, but do fewer allocations.
The new Value.UnsafePointer
method returns the Value's value as an unsafe.Pointer
. This allows callers to migrate from Value.UnsafeAddr
and Value.Pointer
to eliminate the need to perform uintptr to unsafe.Pointer conversions at the callsite (as unsafe.Pointer rules require).
The new MapIter.Reset
method changes its receiver to iterate over a different map. The use of MapIter.Reset
allows allocation-free iteration over many maps.
A number of methods ( Value.CanInt
, Value.CanUint
, Value.CanFloat
, Value.CanComplex
) have been added to Value
to test if a conversion is safe.
Value.FieldByIndexErr
has been added to avoid the panic that occurs in Value.FieldByIndex
when stepping through a nil pointer to an embedded struct.
reflect.Ptr
and reflect.PtrTo
have been renamed to reflect.Pointer
and reflect.PointerTo
, respectively, for consistency with the rest of the reflect package. The old names will continue to work, but will be deprecated in a future Go release.
regexp
now treats each invalid byte of a UTF-8 string as U+FFFD
.
The BuildInfo
struct has two new fields, containing additional information about how the binary was built:
GoVersion
holds the version of Go used to build the binary.Settings
is a slice of BuildSettings
structs holding key/value pairs describing the build.The CPU profiler now uses per-thread timers on Linux. This increases the maximum CPU usage that a profile can observe, and reduces some forms of bias.
strconv.Unquote
now rejects Unicode surrogate halves.
The new Cut
function slices a string
around a separator. It can replace and simplify many common uses of Index
, IndexByte
, IndexRune
, and SplitN
.
The new Clone
function copies the input string
without the returned cloned string
referencing the input string's memory.
Trim
, TrimLeft
, and TrimRight
are now allocation free and, especially for small ASCII cutsets, up to 10 times faster.
The Title
function is now deprecated. It doesn't handle Unicode punctuation and language-specific capitalization rules, and is superseded by the golang.org/x/text/cases package.
The new methods Mutex.TryLock
, RWMutex.TryLock
, and RWMutex.TryRLock
, will acquire the lock if it is not currently held.
The new function SyscallN
has been introduced for Windows, allowing for calls with arbitrary number of arguments. As a result, Syscall
, Syscall6
, Syscall9
, Syscall12
, Syscall15
, and Syscall18
are deprecated in favor of SyscallN
.
SysProcAttr.Pdeathsig
is now supported in FreeBSD.
The Wrapper
interface has been removed.
The precedence of /
in the argument for -run
and -bench
has been increased. A/B|C/D
used to be treated as A/(B|C)/D
and is now treated as (A/B)|(C/D)
.
If the -run
option does not select any tests, the -count
option is ignored. This could change the behavior of existing tests in the unlikely case that a test changes the set of subtests that are run each time the test function itself is run.
The new testing.F
type is used by the new fuzzing support described above. Tests also now support the command line options -test.fuzz
, -test.fuzztime
, and -test.fuzzminimizetime
.
Within a range
pipeline the new {{break}}
command will end the loop early and the new {{continue}}
command will immediately start the next loop iteration.
The and
function no longer always evaluates all arguments; it stops evaluating arguments after the first argument that evaluates to false. Similarly, the or
function now stops evaluating arguments after the first argument that evaluates to true. This makes a difference if any of the arguments is a function call.
The package supports the new text/template and html/template {{break}}
command via the new constant NodeBreak
and the new type BreakNode
, and similarly supports the new {{continue}}
command via the new constant NodeContinue
and the new type ContinueNode
.
The new AppendRune
function appends the UTF-8 encoding of a rune
to a []byte
.