golang

Wrap errors with context using fmt.Errorf and the %w verb, then check them with errors.Is for sentinel values or errors.As for custom error types. Never ignore errors with the blank identifier unless explicitly documented.

Use buffered channels or select statements with ctx.Done() so goroutines can exit when the context is cancelled. Pair this with errgroup or sync.WaitGroup to coordinate worker completion and close channels properly.

Place entry points in cmd/, private application code in internal/, public libraries in pkg/, API definitions in api/, and test fixtures in testdata/. Keep package names short, lowercase, and free of underscores.

Functions should accept interfaces and return concrete structs. Define interfaces in the consumer package where they are used, keeping them small and focused, often with a single method.

Use functional options when a constructor has many optional parameters with sensible defaults. It keeps the API clean and extensible, as shown in server configuration with WithTimeout and WithLogger options.