session is not persisting.killed after redirect

Here is the code.If sign in it goes to /dashboard route. but after I go to other route user session is not persisting(by dd I found this).thanks in advance if you solve, I spent hours on this.

Route::group(['middleware' => 'web'],function(){

  Route::get('/', function () {
    return view('welcome');
  })->name('home');

  Route::get('/dashboard' , [
    'uses' => 'UserController@GetDashboard',
    'as' => 'dashboard'
    ]);

  Route::post('/signin' , [
    'uses' => 'UserController@postSignin',
    'as' => 'signin'
    ]);
});

in my login controller

public function postSignin(Request $request)
  {
   if(Auth::attempt(['email' => $request['email'],'password' =>       $request['password']])) {
  return redirect()->route('dashboard');
   }
  return redirect()->back();
}

via Chebli Mohamed