golang

Wrap errors at each layer with fmt.Errorf and %w, match sentinels with errors.Is, and extract typed errors with errors.AsType. Keep error strings lowercase without punctuation, and use errors.Join to combine independent failures.

Give every goroutine a bounded lifetime using context cancellation, buffered channels, or draining receivers. Diagnose confirmed leaks with the goroutineleak pprof profile and run tests with the -race flag.

It targets Go 1.27+, including generic methods, errors.AsType, testing/synctest, encoding/json/v2, built-in min/max, and range-over-int loops. Legacy patterns like loop variable capture workarounds are flagged as unnecessary on Go 1.22+.

Use encoding/json/v2 for all new code; existing v1 call sites are fine to leave unchanged. The v2 package provides improved performance and a modern Options-based API for marshaling and unmarshaling.

Run benchmarks with -benchmem and -count=10, saving output before and after the change, then compare with benchstat. A result marked with ~ means the difference is indistinguishable from noise.

Never use panic for expected failures like network timeouts or missing files; return errors instead. Panic is only acceptable for programmer errors, impossible conditions, or corrupt invariants such as MustCompile-style initialization.