Make session expiration redirect back to login?

When user logs in and is authenticated, I use Auth::user()->username; to show username of user on dashboard. However, for some reason when session expires the class Auth doesn't seem to work and dashboard page throws error as trying to get property of non-object for Auth::user()->username;. How can I redirect the user back to the login page when he clicks any link or refreshes the page after the session has expired?

via Chebli Mohamed