Update app.py

https://github.com/gradio-app/gradio/issues/1608

app.py

@@ -12,4 +12,9 @@ def read_main():
 
 
 io = gr.Interface(lambda x: "Hello, " + x + "!", "textbox", "textbox")
-app = gr.mount_gradio_app(app, io, path=CUSTOM_PATH)
+
+gradio_app = gr.routes.App.create_app(io)
+
+app.mount(CUSTOM_PATH, gradio_app)
+
+#app = gr.mount_gradio_app(app, io, path=CUSTOM_PATH)