如何在flutter中打印firestore中的值

dependencies:
  flutter:
    sdk: flutter
  firebase_core: ^1.0.0
  cloud_firestore: ^2.0.0

import 'package:firebase_core/firebase_core.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

void printFirestoreValue() async {
  FirebaseFirestore firestore = FirebaseFirestore.instance;
  DocumentSnapshot snapshot = await firestore.collection('collectionName').doc('documentId').get();
  if (snapshot.exists) {
    print(snapshot.data());
  } else {
    print('Document does not exist');
  }
}