title: Flutter - Update duration of countdown timer
body: <p>I am trying to show countdown timer using this resource: <a href="https://stackoverflow.com/a/64312145/13240914">https://stackoverflow.com/a/64312145/13240914</a>:</p>
  <pre><code>TweenAnimationBuilder&lt;Duration&gt;(
    duration: Duration(minutes: 3),
    tween: Tween(begin: Duration(minutes: 3), end: Duration.zero),
    onEnd: () {
      print('Timer ended');
    },
    builder: (BuildContext context, Duration value, Widget? child) {
      final minutes = value.inMinutes;
      final seconds = value.inSeconds % 60;
      return Padding(
        padding: const EdgeInsets.symmetric(vertical: 5),
        child: Text('$minutes:$seconds',
                 textAlign: TextAlign.center,
                 style: TextStyle(
                 color: Colors.black,
                 fontWeight: FontWeight.bold,
                 fontSize: 30)));
      }),
  </code></pre>
  <p>The problem is when duration is still running, I would like to update duration. For example when user click a button, the duration will change from 10 to 20 seconds, but the duration doesn't change to 20 seconds at all... it keeps going to count 10 seconds. Is there a way to update the value of Duration when the duration is still running ?</p>