Go 1.13 (2019-09-03)

Go 1.13 was released in September 2019, improving number literals and error handling, and refining the Modules mechanism.

Major Changes

Language

• Error Wrapping: Go 1.13 introduces a standard error wrapping mechanism, making error handling more flexible and powerful.

  • fmt.Errorf: Supports the %w verb for wrapping errors.
  • New functions in errors package:
    • errors.Is(err, target): Determines if an error chain contains a specific error.
    • errors.As(err, target): Converts an error in the chain to a specific type.
    • errors.Unwrap(err): Unwraps an error, returning the wrapped error.

  if errors.Is(err, os.ErrNotExist) {
      // Handle file not found error
  }

• Number Literal Improvements:

  • Binary Literals: Use 0b or 0B prefix (e.g., 0b1011).
  • Octal Literals: Added 0o or 0O prefix (e.g., 0o660); the old 0 prefix is still valid.
  • Hexadecimal Floating-point: Use 0x prefix and p exponent (e.g., 0x1.0p-1021).
  • Digit Separators: Allows using underscores _ in number literals to improve readability (e.g., 1_000_000, 3.1415_9265).

• Signed Shift Counts: The right operand of shift operators << and >> can now be any signed integer type, no longer limited to unsigned integers.

Toolchain

• GOPROXY Default: The GOPROXY environment variable defaults to https://proxy.golang.org,direct. This means Go uses the Google-maintained module mirror by default.
• GOSUMDB: The sum.golang.org checksum database is enabled by default to verify the integrity of module content.
• GOPRIVATE: Added the GOPRIVATE environment variable to specify private module paths that should not be accessed via the proxy or checksum database.
• go env -w: The go env command now supports the -w flag to set and persist environment variables (e.g., go env -w GOPROXY=direct).

Runtime

• Panic Messages: Runtime panic messages now include the index value and slice length/capacity that caused the out-of-bounds error, facilitating debugging.
• Defer Performance: The performance of defer statements has improved by about 30%.
• sync.Pool: sync.Pool no longer clears all objects during every garbage collection (GC), but retains some objects, thereby reducing allocation peaks after GC.

Standard Library

• TLS 1.3: TLS 1.3 is enabled by default.
• crypto/ed25519: Added crypto/ed25519 package, implementing the Ed25519 signature algorithm.
• time: Duration added Microseconds and Milliseconds methods.
• os: Added UserConfigDir function.

References

For more details, please refer to the official release notes: Go 1.13 Release Notes