package main

import ("fmt"
    "net/http"
    //"log"
    "github.com/gorilla/mux"
   "time"
    //"net/http/fcgi"
   "io/ioutil"
)

 func timer(h http.HandlerFunc) (http.HandlerFunc){
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        startTime := time.Now()  //request time
        h.ServeHTTP(w, r)        //original function called.
        duration := time.Now().Sub(startTime)       //calculation of response    time.
        fmt.Println(duration)
    })
}

func main(){
    r := mux.NewRouter()
    r.HandleFunc("/", timer())
    http.Handle("/",r)
    http.ListenAndServe(":8080",r)
}