Code-Memo

Higher-order functions and middleware

Go has no @decorator syntax. The same idea is a function that accepts a function and returns a function, or middleware wrapping handlers.

Timing wrapper

func timed(fn func()) func() {
	return func() {
		start := time.Now()
		fn()
		_ = time.Since(start)
	}
}

HTTP middleware

func withLogging(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		log.Println(r.Method, r.URL.Path)
		next.ServeHTTP(w, r)
	})
}

Preserving context

When wrapping, forward context, errors, and return values explicitly; there is no generic *args for arbitrary signatures without generics or code generation.

Functional options (constructor pattern)

type Server struct{ addr string; timeout time.Duration }

type Option func(*Server)

func WithTimeout(d time.Duration) Option {
	return func(s *Server) { s.timeout = d }
}

func NewServer(addr string, opts ...Option) *Server {
	s := &Server{addr: addr, timeout: 30 * time.Second}
	for _, o := range opts {
		o(s)
	}
	return s
}

This is a common “configuration decorator” idiom without inheritance.