Added subprotocol match on client

README.md

@@ -15,5 +15,14 @@ A simple websocket client in Golang to debug websocket server.
 
 ### Usages:
 ```bash
-.\SimpleWsClient --addr=wss://echo.websocket.org
+$ ./SimpleWsClient -help
+Usage of ./SimpleWsClient:
+  -addr string
+        http service address (default "ws://echo.websocket.org")
+  -echoDelay uint
+        Delay before echoing back received message from server
+  -protocols string
+        Comma separated list of protocols to use
+
+$ ./SimpleWsClient -addr wss://echo.websocket.org -protocols echo,chat
 ```

main.go

@@ -50,6 +50,23 @@ func main() {
 		log.Fatalf("Unable to dial ws connection to agent %s with error %s\n", address, err)
 	}
 
+	respSubProtocol := conn.Subprotocol()
+	subProtocolMatch := false
+	if len(dialer.Subprotocols) > 0 {
+		for _, val := range dialer.Subprotocols {
+			if val == respSubProtocol {
+				subProtocolMatch = true
+				break
+			}
+		}
+	} else {
+		subProtocolMatch = respSubProtocol == ""
+	}
+
+	if !subProtocolMatch {
+		log.Fatalf("Subprotocol match failed. Server returned subprotocol: '%s'\n", respSubProtocol)
+	}
+
 	log.Println("Connection stabilized")
 	defer conn.Close()