Child controller return 0

In my general controller GeneralController:

use App\Http\Controllers\Controller;
class GeneralController extends Controller
{
    protected $onLine = null;

    public function __construct(Request $request)
    {
        $this->onLine = OnLine::domain($request->domain)->first();
    }
}

In my other controller, extends GeneralController:

use App\Http\Controllers\OnLine\ItemController;
class ItemController extends GeneralController
{
    public function getItem(Request $request)
    {
        dd($this->onLine); // but returns null :(
    }
}

via Chebli Mohamed