Problem using Geolocation from Xlabs sample

I tryed to include in my share project the Geolocation feature from Xlabs sample but i'm having problems when it comes to call the dependencyService.

I have a content page and in there i have my button that has a command like this:

Command = new Command(async () => await GetPosition(), () => Geolocator != null)

the Command leads to:

private IGeolocator Geolocator
        {
            get
            {
                if (_geolocator == null)
                {
                    _geolocator = DependencyService.Get<IGeolocator>();
                    _geolocator.PositionError += OnListeningError;
                    _geolocator.PositionChanged += OnPositionChanged;
                }
                return _geolocator;
            }
        }

and when it should call the _geolocator = DependencyService.Get<IGeolocator>(); nothing happens and _geolocator remains null.

I have all the references from Xlabs and the interface IGeolocator is in my project so why isn't the DependencyService being called??