Laravel Auth ::尝试始终返回登录页面

Question

I am trying to make login page but even if i enter correct mail and password it still returns me login page. If i don't use middleware i can login and go further ,however without middleware i can reach all admin files .

Here is my AuthController;

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use Illuminate\Foundation\Auth\ThrottlesLogins;
use Illuminate\Foundation\Auth\AuthenticatesAndRegistersUsers;
use Illuminate\Support\Facades\Auth;
use Request;
class AuthController extends Controller
{   
 public function __construct()
{
    $this->middleware('guest', ['except' => 'logout']);
}
 protected function validator(array $data)
{
    return Validator::make($data, [
        'email' => 'required|email|max:255|unique:users',
        'password' => 'required|confirmed|min:6',
    ]);
}


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

 public function postLogin(Request $request){

    if (Auth::attempt(['email' => Request::input('email'), 'password' => Request::input('password')])){
        return redirect()->route('admin');
    }else{
        return 'not entered ';
    }
}

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

public function postRegister(Request $request)
{
    return User::create([
        'email' => $request['email'],
        'password' => bcrypt($request['password']),
    ]);
}

Here is my Route;

 Route::group(['prefix' => 'admin'], function () {

Route::group(['middleware' => 'auth'], function () {
    Route::get('index', array('as' => 'admin', 'uses' => 'AdminController@admin'));
    Route::get('doctors', array('as' => 'doctors.index', 'uses' => 'DoctorsController@index'));
    Route::post('doctorstore', array('as' => 'doctors.store', 'uses' => 'DoctorsController@store'));
    Route::post('doctorsmail', array('as' => 'doctors.mail', 'uses' => 'DoctorsController@update'));

});

Route::get('/', array('as' => 'getlogin', 'uses' =>'Auth\AuthController@getLogin'));
Route::post('/', array('as' => 'postlogin', 'uses' =>'Auth\AuthController@postLogin'));

Route::get('/register', array('as' => 'getregister', 'uses' =>'Auth\AuthController@getRegister'));
Route::post('/register', array('as' => 'postregister', 'uses' =>'Auth\AuthController@postRegister'));});