go md5簽名

 var postData = map[string]string{
      "timestamp": "1234567890",
      "app_key":   "XXXX",
      "data":"asdfasdf",
   }
   //私鑰
 var secret = "****************"
 var keys []string
   for k, _ := range postData {
      if k != "token" {
         keys = append(keys, k)
      }
   }
   //1,根據參數名稱的ASCII碼錶的順序排序
 sort.Strings(keys)
   var token string
   for _, v := range keys {
      token += v + "=" + postData[v] + "&"
 }
   //2,全轉小寫(md5(拼裝的字符串後+分配給你的app_secret))
 token = strings.ToLower(fmt.Sprintf("%x", md5.Sum([]byte(strings.Trim(token, "&")+secret))))
   
   fmt.Println(token)