@keung725 you'll likely want to set this session variable in your HomeController@home() method. I don't believe the closure you have included is called by anything.
One tip, you can always return redirect()->back(); or simply return back(); to go to the last visited location from a controller method.
Another tip, it is often nice to store the redirect to a page that requires authentication when sending your users back to the login route (i.e. /auth/login?redirect=/needs/authentication).