Login page get refreshed when I log an admin

I want to redirect the admin user to dasheboard but the Admin-login page always get refreshed, I set up admins tables and ran the migrations and I added one admin with tinkle command

AdminLoginController.php

<?php

       namespace App\Http\Controllers\Admin;

  use App\Http\Controllers\Controller;
   use Illuminate\Foundation\Auth\AuthenticatesUsers;
   use Illuminate\Http\Request;
    use Illuminate\Support\Facades\Auth;
    use App\Admin;




            class  AdminLoginController extends Controller
              {

          public function login(Request $request){

              $this->validate($request,[

       'email'=>'required|email',
       'password'=>'required|min:6'
   ]);
      if ((Auth::guard('admin')->attempt(['email' => $request->email, 'password' => $request->password])) ){

        return redirect()->intended('Admin.dasheboard');
    }
          return redirect()->back();

       }

public function show(){
return view(' Admin.admin-login');
     }
}

My routes:

Route::prefix('admin')->group(function(){
   Route::get('/', 'Admin\AdminController@show');
    Route::get('/login', 'Admin\AdminLoginController@show');
     Route::post('/login', 'Admin\AdminLoginController@login');
      });

Auth.php

'providers' => [
    'users' => [
        'driver' => 'eloquent',
        'model' => App\User::class,
    ],
    'admins' => [
        'driver' => 'eloquent',
        'model' => App\Admin::class,
    ],

     'users' => [
         'driver' => 'database',
         'table' => 'users',
     ], 
    'admins' => [
         'driver' => 'database',
         'table' => 'admins',
     ],
],

For the blade page it has:

   <form action="/admin/login" method="post">

via Chebli Mohamed