Laravel - How to use session and route in config/services.php

I working with facebook login in laravel 5 using laravel/socialite
But in many tutorials have to config in config/services.php like

'facebook' => [
        'client_id' => 'abc',
        'client_secret' => 'def',
        'redirect' => 'http://ghi',
],

But i want dynamic them like user can input them and save to session like

'facebook' => [
        'client_id' => session()->get('client_id'),
        'client_secret' => session()->get('client_secret'),
        'redirect' => route('aa'),
],

But session and route cannot use in config/services.php. How can i make it dynamic thank.

via Chebli Mohamed