public void webSocket(String path, Object handler) {
        addWebSocketHandler(path, new WebSocketHandlerInstanceWrapper(handler));
    }
Maps the given path to the given WebSocket handler instance.
<p>
This is currently only available in the embedded server mode.

@param path    the WebSocket path.
@param handler the handler instance that will manage the WebSocket connection to the given path.
src/main/java/spark/Service.java