build an echo server, but does not work for events or voice images.

server.go

 
 	switch r.Method {
 	case "POST":
-		answerWechatPost(w, r)
+		answerWechatPostEcho(w, r)
+		//answerWechatPost(w, r)
 	case "GET":
 		answerInitialAuth(w, r)
 	default:
 	return
 }
 
+func answerWechatPostEcho(w http.ResponseWriter, r *http.Request) {
+	body, _ := ioutil.ReadAll(r.Body)
+	//fmt.Printf("get body: %s", string(body))
+	s := ReadEncryptedMsg(string(body))
+	//fmt.Printf("to decrypt %s", s.Encrypt)
+	d := Decode(s.Encrypt)
+	fmt.Printf("echo as: \n%s", d)
+
+	e := strings.Replace(d, "ToUserName", "FDDD20170506xyzunique", 2)
+	f := strings.Replace(e, "FromUserName", "ToUserName", 2)
+	g := strings.Replace(f, "FDDD20170506xyzunique", "FromUserName", 2)
+	fmt.Fprint(w, g)
+}
+
 //
 func checkSignature(r *http.Request) bool {
 	rq := r.URL.RawQuery