Laravel 5 want to access auth user id in model

I want to access the currently logged In user ID in the model. So in the model, I have written the codes;

namespace App\Model;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\DB;
use Auth;

and in the method under the model, I used this code: Auth::user()->id However, I receives the error:

Trying to get property of non-object

via Chebli Mohamed