Adding variables from Dart to Google Tag Manager data layer

gtm.dart

    JsObject dataLayer = context['dataLayer'];
    dataLayer ??= new JsObject(context['Array']);
    Map<String, dynamic> productInfo = {
      'name': '1 month subscription',
      'price': 21000,
      'currency': 'HUF'
    };
    dataLayer.callMethod('push', [new JsObject.jsify(productInfo)]);
    context['dataLayer'] = dataLayer;