How to refresh automatically InfoWindow content when dragend

Ionic Framework ionic-v3
1

n this code I try to refresh the content of info window but it fails and opens new info window then I see multiple info windows over marker. this function will called from dragend eventlistener :

addInfoWindow(marker, content){ 
  let infoWindow = new google.maps.InfoWindow({
    content: content
  }); 
     infoWindow.close();
     infoWindow.open(this.map, marker);

}