title: URLSessionTask runs always into an error
body: <p>In my ExtensionDelegate I'm starting a URLSessionTask with following code:</p>
  
  <pre><code>func scheduleNextURLSessionTask() {
      let backgroundConfigObject = URLSessionConfiguration.background(withIdentifier: "myIdentifier")
  
      let backgroundSession = URLSession(configuration: backgroundConfigObject, delegate: self, delegateQueue: nil)
      let retrieveTask = backgroundSession.dataTask(with: URL(string: "https://api.wedtec.net/cryptocoins/index.php?bitcoin&amp;simple")!)
      retrieveTask.resume()
  }
  </code></pre>
  
  <p>My ExtensionDelegate implements URLSessionDataDelegate, of course.
  This runs always into an error. Means </p>
  
  <pre><code>func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?)
  </code></pre>
  
  <p>Will be triggered will following error message:</p>
  
  <blockquote>
    <p>URLSessionTask didCompleteWithError  Optional(Error Domain=NSURLErrorDomain Code=-997 "Lost connection to background transfer service" UserInfo={NSErrorFailingURLKey=<a href="https://api.wedtec.net/cryptocoins/index.php?bitcoin&amp;simple" rel="nofollow noreferrer">https://api.wedtec.net/cryptocoins/index.php?bitcoin&amp;simple</a>, NSErrorFailingURLStringKey=<a href="https://api.wedtec.net/cryptocoins/index.php?bitcoin&amp;simple" rel="nofollow noreferrer">https://api.wedtec.net/cryptocoins/index.php?bitcoin&amp;simple</a>, NSLocalizedDescription=Lost connection to background transfer service}) </p>
  </blockquote>
  
  <p>Any Idea what could be wrong here? scheduleNextURLSessionTask is called from a background process (WKApplicationRefreshBackgroundTask).</p>