Go http handler 中间件

在http的handler处理中加上中间件，可以进行过滤、记录日志、统计和统一返回结果

 package main

 import (
     "fmt"
     "net/http"
     "encoding/json"
 )

 func main() {
     _ = fmt.Println
     http.Handle("/test", FormatReturnHandler(HomeHandler))
     http.ListenAndServe(":8000", nil)
 }

 type normalFunc func(r *http.Request) interface{}

 type Response struct {
     Code int         `json:"code"`
     Data interface{} `json:"data"`
     Msg  string      `json:"msg"`
 }

 func FormatReturnHandler(f normalFunc) http.Handler {
     return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
         fmt.Println(r.URL.Path)

         ret := Response{}
         ret.Data = f(r)
         ret.Code = 0
         ret.Msg = ""
         jsonRet, _ := json.Marshal(&ret)

         w.Write(jsonRet)
     })
 }

 func HomeHandler(r *http.Request) interface{} {
     return r.Host
 }