Dingo "Unauthenticated" error message for logged In users in laravel 5.5

Question

I'm using [Dingo/api][1] laravel package to create an API. I worked with it before and I have not this problem.

this is my routes in the api.php file:

$api = app('Dingo\Api\Routing\Router');
$api->version('v1', ['prefix' => 'v1', 'namespace' => 'App\Http\Controllers'], function ($api) {

    $api->group(['prefix' => 'auth'], function ($api) {
        $api->post('signIn', 'Auth\LoginController@signIn');
    });

    $api->group(['middleware' => 'api.auth'], function ($api) {
        $api->get('signOut', ['uses' => 'Auth\LoginController@signOut']);

        $api->get('test', function () {
            return response()->json(['foo' => 'bar']);
        });
    });

});

/signIn route works fine and respond a token that can used in other protected endpoint like /test and /test directory works fine.

But I want to Sign out a user and call /signOut route it responses this always:

{
    "success": false,
    "message": "Unauthenticated.",
    "status_code": 500
}

This is signOut method in LoginController :

public function signOut()
    {
        //return 'Hiiiii Alll';
        try {
            $token = \Tymon\JWTAuth\Facades\JWTAuth::getToken();
            \Tymon\JWTAuth\Facades\JWTAuth::invalidate($token);
            return [
                'success' => true,
                'message' => 'You Signed Out Successfully'
            ];

        } catch (\Exception $e) {
            return $this->response->error('Something went wrong', 404);
        }
    }

Even when I return a Simple string from that method it does not run, seems problem is in ['middleware' => 'api.auth'] that I used But if it's right why problem does not occurred for test directory that in in the same route group?

Update(solution) :

I found that should change logout to SignOut in __construct() method in LoginController method :

public function __construct()
    {
        $this->middleware('guest')->except('logout');
    }