add fix in upgrade_async example

examples/upgrade_async.py

@@ -26,7 +26,7 @@ app.ws("/*", {
     'message': ws_message,
     'upgrade': ws_upgrade,
     'drain': lambda ws: print('WebSocket backpressure: %s', ws.get_buffered_amount()),
-    'close'lambda ws, code, message: print('WebSocket closed')
+    'close': lambda ws, code, message: print('WebSocket closed')
 })
 app.any("/", lambda res,req: res.end("Nothing to see here!'"))
 app.listen(3000, lambda config: print("Listening on port http://localhost:%d now\n" % (config.port)))