push notification

Request to authorization
Add below code to Appdedelegate

UNUserNotificationCenter.current().delegate = self
UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .badge, .sound]) { (authorized, error) in
   if authorized {
       DispatchQueue.main.async {
           application.registerForRemoteNotifications()
       }
   }
}

Add below code to handle notification when app in background

 func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
   completionHandler([.alert, .sound])
 }