state machine redesign state saving is controlled by main routine,

serveProc procude state transit,

its input is old state, output is new state.

chatState.go

 //Validator function type for validating all wechat inputs
 type Validator func(s chatState) ValidationResult
 
-func saveChatState(state chatState) {
-
+func saveChatState(openID, procedure string, state chatState) (err error) {
+	if isExpired(state.Expire) {
+		//skip saving sate
+		return
+	}
+	_, err = setCurrentState(openID, procedure, state)
+	return
 }

procedure.go

 }
 
 //follow procedure, if there is any
-func serveProc(openID string, input InWechatMsg) (next chatState) {
+func serveProc(state chatState, input InWechatMsg) (next chatState) {
 	return
 }

server.go

 
 	//are we in an existing procedure
 	openID := in.header.FromUserName
-	yes, state := isInProc(openID)
-	if yes {
-		state := serveProc(openID, in)
-		reply = state.response
+	inProc, state := isInProc(openID) //if inside a procedure, resume last saved state
+	if inProc {
+		state = serveProc(state, in) //transit to new state
+		reply = state.response       //xml response
 	} else {
-		state, processed := serveCommand(openID, in) //search or other command
+		state, processed := serveCommand(openID, in) //menu or txt command e.g. search
 		if !processed {                              // transfer to Customer Service (kf)
 			reply = buildKfForwardMsg(openID, "")
+			kfSendTxt(openID, "未识别的命令，已转接校友会理事会，稍后答复您")
 		} else {
 			reply = state.response
 		}
 	}
-	log.Println(reply)
+	log.Println(reply) //instant reply, answering user's request
 	w.Header().Set("Content-Type", "text/xml; charset=utf-8")
 	fmt.Fprint(w, reply)
 
-	saveChatState(state)
+	err := saveChatState(openID, state.Procedure, state)
+	if err != nil {
+		log.Println("Error Cannot Save chat sate")
+		log.Println(err)
+		log.Println(state)
+	}
 	return
 }