Go 1.21 (2023-08-08)

Go 1.21 was released in August 2023, bringing built-in functions, structured logging, and official support for PGO.

Major Changes

Language

• Built-in Functions: Added min, max, and clear built-in functions.
  • min/max: Compute the minimum and maximum values of ordered types.
  • clear: Clears a map or slice (sets elements to zero values).
• Generic Type Inference: Improved type inference for generic functions, supporting argument inference for partially instantiated functions, etc.
• Package Initialization Order: More precisely specified the package initialization order algorithm.

Toolchain

• PGO (Profile-guided Optimization): PGO is now generally available. Compiling with a production profile (defaulting to default.pgo) can significantly improve program performance (typically 2-7%).
• Backward Compatibility & GODEBUG: Improved handling of GODEBUG to better manage version compatibility.
• Go Versioning: Adopted a new version numbering scheme (e.g., Go 1.21.0) and strengthened version constraints in the go directive of go.mod.
• WASI: Preliminary support for WASI (WebAssembly System Interface) preview1 (GOOS=wasip1, GOARCH=wasm).

Standard Library

• log/slog: Introduced the structured logging package log/slog, providing a high-performance, structured logging API.
• slices: Added slices package, providing generic operations for slices (such as Sort, Contains, Clone, Index, etc.).
• maps: Added maps package, providing generic operations for maps (such as Keys, Values, Clone, Copy, etc.).
• cmp: Added cmp package, defining the Ordered constraint and comparison functions.
• testing: Added -test.fullpath option; added testing.Testing() function.
• context: Added WithoutCancel, WithDeadlineCause, WithTimeoutCause, AfterFunc, etc.

References

For more details, please refer to the official release notes: Go 1.21 Release Notes