title: Draw polylines between two or more marker on GMSMapView with Swift3
body: <p>I tried to implement differents solutions for draw polyLines between markers on my GMSMapView but is not working. Do you have others solutions or maybe do you know what's wrong in my code ?</p>
  
  <pre><code>    override func viewDidLoad() {
      super.viewDidLoad()
      let path = GMSMutablePath()
      _data = _modelDelivery.getGarageFromDeliver(refDelivery: _delivery._ref)
      let camera = GMSCameraPosition.camera(withLatitude: 48.853183, longitude: 2.369144, zoom: 13.0)
      self._mapView.camera = camera
  
      let marker = GMSMarker()
      marker.position = CLLocationCoordinate2D(latitude: 48.8531827, longitude: 2.3691443000000163)
      path.add(marker.position)
      marker.title = "Ma position"
      marker.icon = GMSMarker.markerImage(with: UIColor.blue)
      marker.map = self._mapView
  
      for elem in _data {
          let address = elem._adress + ", " + elem._city + ", " + String(elem._zipCode) + ", France"
          let geocoder = CLGeocoder()
          geocoder.geocodeAddressString(address) {
              placemarks, error in
              let placemark = placemarks?.first
              let lat = placemark?.location?.coordinate.latitude
              let lon = placemark?.location?.coordinate.longitude
              let marker = GMSMarker()
              marker.position = CLLocationCoordinate2D(latitude: lat!, longitude: lon!)
              path.add(marker.position)
              marker.title = elem._nameOfGarage
              marker.snippet = elem._adress + "\nOrdre de passege : "
              marker.map = self._mapView
          }
      }
      let rectangle = GMSPolyline(path: path)
      rectangle.strokeWidth = 4
      rectangle.strokeColor = UIColor.red
      rectangle.map = self._mapView
  }
  </code></pre>