title: Value of type 'GADMobileAds' has no member 'start'
body: <p>I'm trying to add a googleAdMob to my app , and I want to start shared instance of GADMobileAds . but it tells me Value of type 'GADMobileAds' has no member 'start'.
  Hint: 
  my Xcode version is 10.1, swift version is 4, iOS target 10 or more, Add appid to GADApplicationIdentifier in plist and I got it with cocoaPod.</p>
  
  <p>here is my code </p>
  
  <pre><code>import UIKit
  import GoogleMobileAds
  
  @UIApplicationMain
  class AppDelegate: UIResponder, UIApplicationDelegate {
      var window: UIWindow?
      func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -&gt; Bool {
          GADMobileAds.sharedInstance().start(completionHandler: nil)
          return true
      }
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/U1aQc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/U1aQc.png" alt="enter image description here"></a></p>