Add graceful leaving for cc server

cc-server/cc-server.yaml

@@ -11,7 +11,7 @@ port: 80
 # a AM/PM marker
 # Example:
 # 11:30AM
-trigger-time: "4:00PM"
+trigger-time: "4:30PM"
 # length of trigger period
 # time can be represented with its symbols
 # Example:

cc-server/web/web.go

@@ -24,15 +24,16 @@ func wsHandler(w http.ResponseWriter, r *http.Request) {
 	for {
 		mt, message, err := conn.ReadMessage()
 		if err != nil {
+			if e, ok := err.(*websocket.CloseError); ok &&
+				(e.Code == websocket.CloseNormalClosure ||
+					e.Code == websocket.CloseNoStatusReceived) {
+				log.Infof("Connect %s leaving", r.RemoteAddr)
+				break
+			}
 			log.Errorf("fatal read error: %s", err)
 			break
 		}
 
-		// if connection closes
-		if mt == websocket.CloseNormalClosure {
-			break
-		}
-
 		// init handler
 		if mt == websocket.TextMessage && string(message[:5]) == "init:" {
 			err = handler.Init(message, conn)