golang-patterns

Wrap errors with context using fmt.Errorf and the %w verb, define sentinel errors with errors.New for common cases, and create custom error types for domain-specific failures. Check errors with errors.Is and errors.As rather than string comparison, and never ignore errors with the blank identifier.

Use buffered channels or select statements with ctx.Done() so goroutines can exit when the context is cancelled. An unbuffered channel send blocks forever if no receiver exists, which is the most common leak source.

Functions should accept interfaces as parameters and return concrete struct types. Define small, focused interfaces in the consumer package where they are used, not in the provider package.

The functional options pattern uses variadic Option functions to configure a struct, letting callers set only the fields they need while defaults apply to the rest. It avoids long constructor parameter lists and keeps APIs extensible.

Use errgroup when you need to run multiple goroutines and collect the first error, since it combines WaitGroup coordination with error propagation and context cancellation. Plain WaitGroup only waits for completion without error handling.

Enable errcheck, gosimple, govet, ineffassign, staticcheck, unused, gofmt, and goimports in golangci-lint. Run go vet and go test -race alongside these for static analysis and race detection.