Chains middleware adapters into an http server

adapter_pattern.go

type Adapter func(http.Handler) http.Handler

func Metric() Adapter {
	return func(h http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			log.Println("Metric")
			h.ServeHTTP(w, r)
		})
	}
}

func Adapt(h http.Handler, adapters ...Adapter) http.Handler {
	for _, adapter := range adapters {
		h = adapter(h)
	}
	return h
}

func main() {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /", handleHello)

	http.ListenAndServe(":8080", Adapt(mux, Metric()))
}

func handleHello(w http.ResponseWriter, r *http.Request) {
	w.Write([]byte("Basic API"))
}