问调用API后，swift 3无法更新markerinfowindow内容

EN

func mapView(_ mapView: GMSMapView, markerInfoWindow marker: GMSMarker) -> UIView? {
        let customInfoWindow = Bundle.main.loadNibNamed("customInfoWindown", owner: self, options: nil)?[0] as! CustomInfoWindowns
        customInfoWindow.title = "This is title"
        return customInfoWindow
}

func mapView(_ mapView: GMSMapView, markerInfoWindow marker: GMSMarker) -> UIView? {
        let customInfoWindow = Bundle.main.loadNibNamed("customInfoWindown", owner: self, options: nil)?[0] as! CustomInfoWindowns
        let id = marker.userData as? String 
        UserManager.sharedInstance.getUserInfo(id, onComplete: {(content, error) in
            let userModel = UserModel.convertStringToUserModel(content!)
            DispatchQueue.main.async {                
                 customInfoWindow.title = userModel.name // this code didn't work
            }
        } )            
        return customInfoWindow
}