The argument type 'Future<List<PieChartSectionData>>' can't be assigned to the parameter type 'List<PieChartSectionData>?' – Flutter

I want to display a chart that retrieve from firebase firestore but its says that

The argument type ‘Future<List<PieChartSectionData>>’ can’t be assigned to the parameter type ‘List<PieChartSectionData>?’ on the line sections: showingSections();

. Here are my codes,

children: <Widget>[
                                      const SizedBox(height: 18),
                                      Expanded(
                                        child: AspectRatio(
                                          aspectRatio: 1,
                                          child: PieChart(
                                            PieChartData(
                                              pieTouchData: PieTouchData(
                                                touchCallback:
                                                    (FlTouchEvent event,
                                                        pieTouchResponse) {},
                                              ),
                                              borderData: FlBorderData(
                                                  //show: false,
                                                  ),
                                              sectionsSpace: 0,
                                              centerSpaceRadius: 40,
                                              sections: showingSections(), // this is the error //
                                            ),
                                          ),
                                        ),
                                      ),
                                      Column(
                                        mainAxisAlignment:
                                            MainAxisAlignment.end,
                                        crossAxisAlignment:
                                            CrossAxisAlignment.start,
                                        children: const <Widget>[
                                          Indicator(
                                            color: Colors.blue,
                                            text: 'Fiest',
                                            isSquare: true,
                                          ),
                                        ],
                                      ),
                                    ],

this is my function,

Future<List<PieChartSectionData>> showingSections() async {
    int count = await subuhPrayedOnTime();
    int count2 = await subuhPrayedLate();
    double percentage1 = count * 0.4;
    double percentage2 = count2 * 0.10;

    return [
      PieChartSectionData(
        color: Colors.blueAccent,
        value: percentage1,
        title: '${percentage1.toStringAsFixed(0)}%',
        radius: 60,
        titleStyle: const TextStyle(
          fontSize: 20,
          fontWeight: FontWeight.bold,
          color: Colors.black,
          //shadows: shadows,
        ),
      ),
      PieChartSectionData(
        color: Colors.blueAccent,
        value: percentage2,
        title: '${percentage2.toStringAsFixed(0)}%',
        radius: 60,
        titleStyle: const TextStyle(
          fontSize: 20,
          fontWeight: FontWeight.bold,
          color: Colors.black,
          //shadows: shadows,
        ),
      ),
    ];

    
  }