### [READ] Step 1: Are you in the right place? Yes ### [REQUIRED] Step 2: Describe your environment * Xcode version: 10.1 (10B61) * Firebase SDK version: 5.17.0 * Firebase Component: Core * Component version: 5.3.0 ### [REQUIRED] Step 3: Describe the problem #### Steps to reproduce: following is in my pod file of a new project ``` pod 'Firebase/Core', '~> 5.17.0' ``` #### Relevant Code: Completion handler **NEVER** get called. Nor result or error ``` import Firebase import UIKit @UIApplicationMain class AppDelegate: UIResponder, UIApplicationDelegate { var window: UIWindow? func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool { FirebaseApp.configure() InstanceID.instanceID().instanceID { (result, error) in // Not called } return true } } ``` But if add delay, like that: ``` DispatchQueue.main.asyncAfter(deadline: (.now() + 0.3)) { InstanceID.instanceID().instanceID { (result, error) in // Get called } } ``` All is work