Laravel 5.2 - Using Auth::check() not working in MIddleware

I am trying to make a middleware for different type of users in my Laravel 5.2 app. So, what is I am doing is making different middlewares for different users.

As far as I am knowing Auth::check() will not work without musing middleware web from here.

So, what I have done is-

routes.php

Route::group(['middleware' => ['web','admin']], function ()
{
    //suspend, activate, delete
    Route::get('users', [
        'uses'          => 'AdminController@users',
        'as'            => 'users'
    ]);

    //Edit,activate,suspend, delete
    Route::get('articles', [
        'uses'          => 'AdminController@articles',
        'as'            => 'articles'
    ]);
});

AdminMiddleware.php

<?php

namespace App\Http\Middleware;

use Closure;
use Auth;

class AdminMiddleware
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        if (Auth::check())
        {
            return Auth::user();
            //return redirect('home');
        }
        else
        {
            return redirect('login');
        }

        //now return the valid request
        return $next($request);
    }
}

Kernel.php

protected $routeMiddleware = [
    'auth'          => \App\Http\Middleware\Authenticate::class,
    'admin'         => \App\Http\Middleware\AdminMiddleware::class,
    'user'          => \App\Http\Middleware\UserMiddleware::class,
    'auth.basic'    => \Illuminate\Auth\Middleware\AuthenticateWithBasicAuth::class,
    'guest'         => \App\Http\Middleware\RedirectIfAuthenticated::class,
    'throttle'      => \Illuminate\Routing\Middleware\ThrottleRequests::class,
];

AdminController.php

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;

use App\Http\Requests;
use App\Http\Controllers\Controller;

class AdminController extends Controller
{
    public function users()
    {
        return view('admin.users');
    }

    public function articles()
    {
        return view('admin.articles');
    }
}

But I am getting this error-

when "return Auth::user();" called inside middleware, "return Auth::user();" is working in other place (view and controllers) but not working like old versions of Laravel.

Can anyone please help?

via Chebli Mohamed