Laravel Auth::user() return null after login using guard('admin')

I have set the guard as admin like return Auth::guard('admin'). it can get data from the table 'admins' but after attempt Auth::user() return null

LoginController =============== public function backendLogin(Request $request) { $this->validateLogin($request); if ($this->hasTooManyLoginAttempts($request)) { $this->fireLockoutEvent($request); return $this->sendLockoutResponse($request); } if ($this->attemptLogin($request)) { return $this->sendLoginResponse($request); } $this->incrementLoginAttempts($request); return $this->sendFailedLoginResponse($request); } protected function guard() { return Auth::guard('admin'); } config/auth.php =============== 'guards' => [ 'web' => [ 'driver' => 'session', 'provider' => 'users', ], 'admin' => [ 'driver' => 'session', 'provider' => 'admins', ], 'api' => [ 'driver' => 'token', 'provider' => 'users', 'hash' => false, ], ], 'providers' => [ 'users' => [ 'driver' => 'eloquent', 'model' => App\User::class, ], 'admins' => [ 'driver' => 'eloquent', 'model' => App\Admin::class, ], ], 

I have tried many type of

auth()->guard('admin')->attempt($credentials); Auth::guard('admin')->attempt($credentials); 

but still cannot login.