How to create a login page before google outh

import panel as pn

template = pn.template.FastListTemplate(

    title="My App",

)

template.main.append(pn.pane.Markdown("## Main App"))

template_login = pn.template.FastListTemplate(
    title="Login",
)

def login_view():

    pn.state.location.pathname = '/main_app'
    pn.state.location.reload = True

template_login.main.append(pn.pane.Markdown("Use the button below to login to the app using google account"))

button = pn.widgets.Button(name="Login", button_type="primary")

button.on_click(login_view)

template_login.main.append(button)

pn.serve(
    {
        "/": template_login,
        "/main_app": template,
    },
    port=5006,
    dev=True,
    show=True,
    websocket_origin="localhost:5006",
    allow_websocket_origin=["localhost:5006"],
    autoreload=False,
    oauth_provider="google",
    cookie_secret="xxxx",
    oauth_key="xxx",
    oauth_secret="xxxxx",
    oauth_encryption_key="xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
    oauth_redirect_uri="/main_app",
)

I have the above app, I want to have a page where the user clicks on a button that directs him to the main app that cannot be accessed only after the users authenticate using their google account.

But this code does not work