middleware.go

package main

import (
	"log"
	"net/http"
	"os"
)

type Adapter func(http.Handler) http.Handler

func main() {
	indexHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("indexHandler say hello."))
	})
	indexHandler = Adapte(indexHandler, logHandler(log.New(os.Stdout, "handler:", 0)),
		logHandler(log.New(os.Stdout, "log:", 0))).(http.HandlerFunc)
	http.ListenAndServe(":8003", indexHandler)
}

func Adapte(handler http.Handler, ads ...Adapter) http.Handler {
	for _, ad := range ads {
		handler = ad(handler)
	}
	return handler
}

func logHandler(logger *log.Logger) Adapter  {
	return func(handler http.Handler) http.Handler {
		return  http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			logger.Printf("log someting.")
			handler.ServeHTTP(w, r)
		})
	}
}