import 'package:map_view/map_view.dart';
import 'package:map_view/polyline.dart';
...
MapView mapView = MapView();
mapView.addPolyline(Polyline('my_polyline', [
  Location(45.52309483308097, -122.67339684069155),
  Location(45.52298442915803, -122.66339991241693),
]));