title: Timer is not worked in background flutter
body: <p>This code is not printed, when app go to background in iOS.</p>
  <pre><code>Timer.periodic(Duration(seconds: 1), (timer) { print('timer'); }
  </code></pre>
  <p>I need to save state to database and play sound after finishing timer. But timer counter minimum is 1 minute. So it means at minimum after 1 minute timer will be finished. This value will be set by user. During this interval device maybe locked. Even if device is locked, app must save state after finishing timer.</p>