Go 1.20 (2023-02-01)

Go 1.20 was released in February 2023, focusing on performance optimization, compiler improvements, and standard library enhancements.

Major Changes

Language

• Slice to Array Conversion: Support for converting slices directly to arrays (Go 1.17 already supported conversion to array pointers).

  s := []int{1, 2, 3}
  a := [3]int(s) // copy

• unsafe Package: Added SliceData, String, and StringData functions, providing implementation-independent capabilities for constructing and deconstructing slices/strings.

• Comparable Constraint: The comparable constraint can now be satisfied by ordinary interfaces, even if the type arguments are not strictly comparable (comparison may panic at runtime).

Toolchain

• PGO (Preview): Introduced preview support for Profile-guided Optimization (PGO). Using the -pgo flag, the compiler can use runtime profile information for specific optimizations (such as more aggressive inlining), improving performance by about 3-4%.

• go build -cover: Support for collecting code coverage for binaries, not just tests.

  go build -cover -o myapp
  GOCOVERDIR=covdata ./myapp

• No Precompiled Standard Library: $GOROOT/pkg no longer stores precompiled archive files for the standard library. Standard library packages are now built and cached on demand like other packages, reducing the size of the Go distribution.

• vet Tool: Improved detection of loop variable capture (for nested functions) and added detection for time format errors.

Performance

• Compiler: Optimized inlining and bounds check elimination, improving code execution efficiency. Build speed improved by about 10% compared to Go 1.19.
• Memory Management: Optimized internal data structures for garbage collection, reducing memory overhead and improving CPU performance.

Standard Library

• errors: Support for wrapping multiple errors.
  • fmt.Errorf supports multiple %w.
  • Added errors.Join function for combining multiple errors.
• context: Added WithCancelCause and Cause, allowing specific cancellation causes to be passed and retrieved when cancelling a context.
• crypto/ecdh: Added crypto/ecdh package, providing explicit support for NIST curves and Curve25519.
• net/http:
  • Added ResponseController type for accessing extended features of ResponseWriter (such as SetReadDeadline, SetWriteDeadline).
  • httputil.ReverseProxy added Rewrite hook, replacing Director, providing more powerful request rewriting capabilities.
• time: Added constants DateTime, DateOnly, TimeOnly. Added Time.Compare method.

Platform Support

• Windows: Go 1.20 is the last version to support Windows 7, 8, Server 2008, and Server 2012.
• macOS: Go 1.20 is the last version to support macOS 10.13 High Sierra and 10.14 Mojave.
• FreeBSD/RISC-V: Added experimental support for GOOS=freebsd, GOARCH=riscv64.

References

For more details, please refer to the official release notes: Go 1.20 Release Notes