我尝试登录时重定向了同一页面

Question

Page loginController

<?php
     namespace App\Http\Controllers;
    use App\Http\Controllers\Controller;
    use Illuminate\Foundation\Auth\AuthenticatesUsers;
    use Illuminate\Http\Request;
    use Auth;

    class loginController extends Controller
    {
    use AuthenticatesUsers;

        protected $username = 'username';
        protected $redirectTo = '/dashboard';
        protected $guard   = 'web';

      public function getLogin()
      {
        if (Auth::guard('web')->check()) 
        {
            return redirect()->route('dashboard');
        }
        return view('login');
      }
      public function postlogin(Request $request)
      {
        $auth = Auth::guard('web')->attempt(['username'=>$request->username,'password'=>$request->password,'active'=>1]);

        if ($auth) 
        {
            return redirect()->route('dashboard');
        }
            return redirect()->route('/');
      }

      public function getLogout()
      {
        Auth::guard('web')->logout();
        return redirect()->route('/');
      }

    }

在web.php

 Route::get('/' , ['as' => '/' , 'uses'=> 'loginController@getlogin']);
                Route::post('/login', ['as' => 'login', 'uses'=> 'loginController@postlogin']);


            Route::group(['middleware' =>['authen','roles']], function () {
                    Route::get('/dashboard',['as'=>'dashboard', 'uses'=> 'dashboardController@dashboard']);
                    Route::get('/logout' ,['as'=>'logout', 'uses'=> 'loginController@getLogout']);
                 });

在authen.php

<?php
    namespace App\Http\Middleware;
    use Closure;
    use Illuminate\Support\Facades\Auth;

    class Authen
    {
        public function handle($request, Closure $next ,$guard ='web')
        {
            if (!Auth::guard($guard)->check()) 
            {
              return redirect()->route('/');   
            }
            return $next($request);
        }
    }

在dashboardController

<?php
        namespace App\Http\Controllers;
        use Illuminate\Http\Request;
        class dashboardController extends Controller
        {
             public function __cinstruct()
            {
                $this->middleware('web');
            }
            public function dashboard()
            {
                return view('layouts.master');
            }
        }

我是laravel的新手，当我尝试登录时重定向到同一页面（登录）..如何登录，我的问题在哪里。我该怎么办？