_content/blog: add go1.20
Announce Go 1.20 (to be posted with the release, planned for
beginning of February).
Change-Id: I7c8f057157357a1eae57915dda30abc68a99e915
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Reviewed-by: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
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+---
+title: Go 1.20 is released!
+date: 2023-02-01
+by:
+- Robert Griesemer, on behalf of the Go team
+summary: Go 1.20 brings PGO, faster builds, and various tool, language, and library improvements.
+---
+
+Today the Go team is thrilled to release Go 1.20,
+which you can get by visiting the [download page](/dl/).
+
+Go 1.20 benefited from an extended development phase,
+made possible by earlier broad testing and improved overall stability
+of the code base.
+
+We're particularly excited to launch a preview of [profile-guided optimization](/doc/pgo)
+(PGO), which enables the compiler to perform application- and
+workload-specific optimizations based on run-time profile information.
+Providing a profile to `go build` enables the compiler to speed up typical
+applications by around 3–4%, and we expect future releases to benefit even more
+from PGO.
+Since this is a preview release of PGO support, we encourage folks to try it out,
+but there are still rough edges which may preclude production use.
+
+Go 1.20 also includes a handful of language changes,
+many improvements to tooling and the library, and better overall performance.
+
+## Language changes
+
+- The predeclared [`comparable`](ref/spec#Type_constraints) constraint is
+now also [satisfied](/ref/spec#Satisfying_a_type_constraint) by
+ordinary [comparable types](/ref/spec#Comparison_operators), such as interfaces,
+which will simplify generic code.
+- The functions `SliceData`, `String`, and `StringData` have been added
+to package [`unsafe`](/ref/spec#Package_unsafe). They complete the set of functions
+for implementation-independent slice and string manipulation.
+- Go's type conversion rules have been extended to permit direct conversion
+[from a slice to an array](/ref/spec#Conversions_from_slice_to_array_or_array_pointer).
+- The language specification now defines the exact order in which array elements
+and struct fields are [compared](/ref/spec#Comparison_operators).
+This clarifies what happens in case of panics during comparisons.
+
+## Tool improvements
+
+- The [`cover` tool](/testing/coverage) now can collect coverage profiles of whole programs,
+not just of unit tests.
+- The [`go` tool](/cmd/go) no longer relies on pre-compiled standard library
+package archives in the `$GOROOT/pkg` directory, and they are no longer
+shipped with the distribution, resulting in smaller downloads.
+Instead, packages in the standard library are built as needed and cached
+in the build cache, like other packages.
+- The implementation of `go test -json` has been improved
+to make it more robust in the presence of stray writes to `stdout`.
+- The `go build`, `go install`, and other build-related
+commands now accept a `-pgo` flag enabling profile-guided optimizations
+as well as a `-cover` flag for whole-program coverage analysis.
+- The `go` command now disables `cgo` by default on systems without a C toolchain.
+Consequently, when Go is installed on a system without a C compiler, it will
+now use pure Go builds for packages in the standard library that optionally use cgo,
+instead of using pre-distributed package archives (which have been removed,
+as noted above).
+- The [`vet` tool](/cmd/vet) reports more loop variable reference mistakes
+that may occur in tests running in parallel.
+
+## Standard library additions
+
+- The new [`crypto/ecdh`](/pkg/crypto/ecdh) package provides explicit support for
+Elliptic Curve Diffie-Hellman key exchanges over NIST curves and Curve25519.
+- The new function [`errors.Join`](/pkg/errors#Join) returns an error wrapping a list of errors
+which may be obtained again if the error type implements the `Unwrap() []error` method.
+- The new [`http.ResponseController`](/pkg/net/http#ResponseController) type
+provides access to extended per-request functionality not handled by the
+[`http.ResponseWriter`](/pkg/net/http#ResponseWriter) interface.
+- The [`httputil.ReverseProxy`](/pkg/net/http/httputil#ReverseProxy)
+forwarding proxy includes a new `Rewrite` hook function, superseding the
+previous `Director` hook.
+- The new [`context.WithCancelCause`](/pkg/context#WithCancelCause) function
+provides a way to cancel a context with a given error.
+That error can be retrieved by calling the new
+[`context.Cause`](/pkg/context#Cause) function.
+- The new [`os/exec.Cmd`](/pkg/os/exec#Cmd) fields [`Cancel`](/pkg/os/exec#Cmd.Cancel)
+and [`WaitDelay`](/pkg/os/exec#Cmd.WaitDelay) specify the behavior of the
+`Cmd` when its associated `Context` is canceled or its process exits.
+
+## Improved performance
+
+- Compiler and garbage collector improvements have reduced memory overhead
+and improved overall CPU performance by up to 2%.
+- Work specifically targeting
+compilation times led to build improvements by up to 10%.
+This brings build speeds back in line with Go 1.17.
+
+When [building a Go release from source](/doc/install/source),
+Go 1.20 requires a Go 1.17.13 or newer release.
+In the future, we plan to move the bootstrap toolchain forward approximately
+once a year.
+Also, starting with Go 1.21, some older operating systems will no longer be supported:
+this includes Windows 7, 8, Server 2008 and Server 2012,
+macOS 10.13 High Sierra, and 10.14 Mojave.
+On the other hand, Go 1.20 adds experimental support for FreeBSD on RISC-V.
+
+For a complete and more detailed list of all changes see the [full release notes](/doc/go1.20).
+
+Thanks to everyone who contributed to this release by writing code, filing bugs,
+sharing feedback, and testing the release candidates. Your efforts helped
+to ensure that Go 1.20 is as stable as possible.
+As always, if you notice any problems, please [file an issue](/issue/new).
+
+Enjoy Go 1.20!
