How to set engagement id for a guided engagement

I am using the guided engagement in a flutter mobile application and I need to configure the next button of a dialog to execute a callback written in code. I have initialized the gainsight code as:
 

final EngagementCallback engagementCallback = GlobalEngagementCallback();
await GainsightPX.instance.initialise(configurations, engagementCallback);

And 

class GlobalEngagementCallback implements EngagementCallback {
  @override
  bool onCallback(EngagementMetaData engagementMetaData) {
    print(engagementMetaData.toString());
    if (engagementMetaData.actionType == 'link') {
      Utils.displayToast(text: engagementMetaData.toString());
    }
    return true;
  }
}

Now, if I click on the In the `onCallback` method, the engagementMetadata has empty engagementId and engagementName, though the action related properties are getting populated fine.
Now, I need to identify the specific engagement and do some custom operation. Could you please guide on how can I do that.