Laravel Facebook Login : Error app_id is required

I'm using laravel 5.1, I want to add facebook social login to my page, but it is returning error

The parameter app_id is required

routes.php

Route::get('/redirect', 'UserController@redirect');
Route::get('/callback', 'UserController@callback');

UserController

public function redirect(){
    return Socialite::driver('facebook')->redirect();
}

Composer.json

"require": {
    "php": ">=5.5.9",
    "laravel/framework": "5.1.*",
     "laravel/socialite": "^2.0",
}

Config/Services.php

'facebook' => [
    'client_id' => '222221956976734',
    'client_secret' => 'a5acf8e8e01745d47rer829a0094vfvf',
    'redirect' => 'http://localhost/myproject/public/callback',
],

HTML

<a href="" style="background-color : rgb(59,89,152)" class="btn blue_btn_big">Login via Facebook</a>

What I have missed here..Any help is much appreciated..

via Chebli Mohamed