Go 1.15 (2020-08-11)

Go 1.15 was released in August 2020, mainly improving the linker and runtime performance, and optimizing the toolchain.

Major Changes

Toolchain

• Linker Improvements: Go 1.15 includes major improvements to the linker, significantly reducing resource usage and improving code robustness.
  • Performance: Link speed improved by 20% and memory usage reduced by 30% for large Go programs.
  • Binary Size: Generated binary size reduced by an average of 5% by eliminating unused type metadata.
• GOPROXY Enhancements: The GOPROXY environment variable now supports skipping proxies that return errors.
  • Separated by pipes | (e.g., https://proxy1|https://proxy2): If the first proxy returns any error, try the next one.
  • Separated by commas ,: Only try the next one if a 404/410 is returned.
• GOMODCACHE: Added GOMODCACHE environment variable, allowing users to customize the location of the module cache (default is $GOPATH/pkg/mod).
• Vet Checks:
  • string(int): vet now warns about conversions of the form string(x) where x is an integer type (not rune/byte). It is recommended to use string(rune(x)) or strconv.Itoa(x).
  • Interface Conversions: Checks for interface type assertions that can never succeed.

Runtime

• Small Object Allocation: Improved performance of small object allocation on high core counts, reducing worst-case latency.
• Panic Output: panic can now print values of more types (such as booleans, complex numbers, integers, strings), not just addresses.
• Signal Handling: On Unix systems, if a program receives SIGSEGV, SIGBUS, or SIGFPE and does not handle it, it will now reliably crash and print a stack trace.

Standard Library

• Embedded Time Zone Data (time/tzdata): Added time/tzdata package, allowing the time zone database to be embedded in the program.
  • Usage: Import import _ "time/tzdata" or build with -tags timetzdata.
  • Effect: Allows the program to correctly handle time zone information in environments without a system time zone database (such as some container images). However, this increases the binary size by about 800 KB.
• X.509 CommonName Deprecation: The crypto/x509 package now treats the CommonName field as deprecated by default.
  • Behavior Change: If a certificate does not have Subject Alternative Names (SANs), Go will no longer verify CommonName as a hostname.
  • Temporary Reversion: The old behavior can be temporarily restored by setting the environment variable GODEBUG=x509ignoreCN=0.
• testing:
  • t.TempDir(): Automatically creates and cleans up a temporary directory.
  • t.Deadline(): Gets the deadline for the test timeout.
• sync:
  • Map.LoadAndDelete: Atomically loads and deletes a key value.
• net/url:
  • URL.Redacted(): Returns a URL string with the password hidden.
• time:
  • Ticker.Reset(): Allows resetting the Ticker interval.
• database/sql:
  • DB.SetConnMaxIdleTime: Sets the maximum idle time for connections in the connection pool.

References

For more details, please refer to the official release notes: Go 1.15 Release Notes