Jointtype of google_map_flutter not working in IOS

Question

Im using google_map_flutter for implementing map,but i need to use the property jointype of polyline and i changed the jointype to round but it doesnot make any change. The exact use of polyline is for i need to curve the joints of polyline whenever turn occurs.

 Polyline(
        polylineId: const PolylineId('seg1'),
        points: routes,
        jointType: JointType.round,
        geodesic: false,
        color: Colors.blue,
        width: 10,
      )