Trying to call a Future<void> function() in onPressed option in Flutter

Question

I am trying to show an Unity Ad when a button is pressed. I tried a few things but I can't fix it.

Here are my code snippets:

main.dart ->

Align(
                    alignment: Alignment.bottomCenter,
                    child: Padding(
                        padding: EdgeInsets.all(8.0),
                        child: ElevatedButton(
                          onPressed: () async {
                            await AdManager.showIntAd();
                            },
                          child: Text('Doniraj'),
                      )),),

AdManager.dart ->

  static Future<void> showIntAd() async {
   UnityAds.showVideoAd(
    placementId: AdHelper.interstitialId,
    onStart: (placementId) => print('Video Ad $placementId started'),
    onClick: (placementId) => print('Video Ad $placementId click'),
    onSkipped: (placementId) => print('Video Ad $placementId skipped'),
    onComplete: (placementId) async {
      await loadUnityIntAd();
    },
    onFailed: (placementId, error, message) async {
      await loadUnityIntAd();
    });

}

I appreciate your suggestions