Unable to load custom tile on google map using iOS swift

Question

I'm trying to use custom tiles as overlay for google maps. "https://tile.example.com/hot/{z}/{x}/{y}.png" I used "GMSTileURLConstructor", but unable to load map on mobile app. I cannot seem to find anything online. Thanks in advance.

I used the following lines.

class ViewController: UIViewController, GMSMapViewDelegate{

    let urls: GMSTileURLConstructor = {z,x,y in
       let url = "https://tile.example.com/hot/{z}/{x}/{y}.png"
       print(url)
       return URL(string: url)
   }