Update zh/04.4.md

more readable code with token

zh/04.4.md

@@ -21,10 +21,10 @@
 func login(w http.ResponseWriter, r *http.Request) {
 	fmt.Println("method:", r.Method) //获取请求的方法
 	if r.Method == "GET" {
-		crutime := time.Now().Unix()
-		h := md5.New()
-		io.WriteString(h, strconv.FormatInt(crutime, 10))
-		token := fmt.Sprintf("%x", h.Sum(nil))
+		timestamp := strconv.Itoa(time.Now().Nanosecond())
+		hashWr := md5.New()
+		hashWr.Write([]byte(timestamp))
+		token := fmt.Sprintf("%x", hashWr.Sum(nil))
 
 		t, _ := template.ParseFiles("login.gtpl")
 		t.Execute(w, token)