import 'package:url_launcher/url_launcher.dart';

try {
  launch("market://details?id=" + appPackageName);
} on PlatformException catch(e) {
    launch("https://play.google.com/store/apps/details?id=" + appPackageName);        
} finally {
  launch("https://play.google.com/store/apps/details?id=" + appPackageName);        
}