Can anyone tell me how to add the geolocator listen position to a google marker?

I am trying to make a navigation marker on google map, for the user location I am using geolocator pub dev with the listen function however it returned as a Position? and since it have the posibility of null, it can't be used directly can anyone tell me how to do it ?

Position? listenToLocation()
  {
    Position? userposition;
    final LocationSettings _locationSettings = LocationSettings(accuracy: LocationAccuracy.high,distanceFilter: 100);
    userStreamlocation = Geolocator.getPositionStream(locationSettings: _locationSettings).listen(
    (userposition) {
        print(userposition == null ? 'Unknown' : '${userposition.latitude.toString()}, ${userposition.longitude.toString()}');
        setState(){
          streamResult=userposition;
        }
    });
    return userposition;
  }

I am able to fix this after finding out that the marker didn't got updated because it is in a different state than the main widget, I fix it trough the use of the statebuilder widget, here's the code snip

StatefulBuilder(
        builder: (context, setMapState) {
          setMapState(
            () {},
          );

          void _whenMapCreated(GoogleMapController controller) async {
            //debugPrint('>>>>>>>>> onMapCreated');
            mapController = controller;
            _Navmarkers.clear();
            _navPolylines.clear();
            var direction =
                await LocationService().getDirectionNoWP(userOrigin, userGoal);
            _setPolylines(direction['polyline_decoded']);
            setMapState(
              () {},
            );
          }

          return Column(children: [
            Expanded(
                child: GoogleMap(
              mapType: MapType.normal,
              initialCameraPosition:
                  CameraPosition(target: _kGooglePlex, zoom: 11),
              markers: _Navmarkers,
              polylines: _navPolylines,
              onMapCreated: _whenMapCreated,
            )),
            Row(
              children: [
                ButtonBar(
                  children: [
                    IconButton(
                        onPressed: () {
                          Position? userposition;

                          const LocationSettings _locationSettings =
                              LocationSettings(
                            accuracy: LocationAccuracy.high,
                            distanceFilter: 100,
                          );
                          userStreamlocation = Geolocator.getPositionStream(
                                  locationSettings: _locationSettings)
                              .listen((userposition) {
                            _Navmarkers.clear();
                            _Navmarkers.add(Marker(
                                markerId: MarkerId('User'),
                                position: LatLng(userposition.latitude,
                                    userposition.longitude),
                                icon: BitmapDescriptor.defaultMarkerWithHue(
                                    BitmapDescriptor.hueRose)));
                            setMapState(() {                            
                            });                            
                          });
                        },
                        icon: Icon(Icons.navigation)),
                    IconButton(
                        onPressed: () {
                          setMapState(
                            () {                             
                            },
                          );
                        },
                        icon: Icon(Icons.refresh)),
                    IconButton(
                        onPressed: () {
                          dispose();
                        },
                        icon: Icon(Icons.stop))
                  ],
                )
              ],
            )
          ]);
        },
      ),

This way the googlemap have its own state and can be refreshed