如何在带有标记的flutter中使用json_serializable，以便在GoogleMap中使用它们？

dependencies:
  json_annotation: ^4.4.0
  json_serializable: ^4.1.0

import 'package:json_annotation/json_annotation.dart';

part 'location.g.dart';

@JsonSerializable()
class Location {
  final double latitude;
  final double longitude;

  Location({required this.latitude, required this.longitude});

  factory Location.fromJson(Map<String, dynamic> json) =>
      _$LocationFromJson(json);

  Map<String, dynamic> toJson() => _$LocationToJson(this);
}

flutter pub run build_runner build

import 'dart:convert';
import 'package:flutter/services.dart' show rootBundle;

Future<List<Location>> fetchLocations() async {
  // 获取包含JSON数据的字符串
  String jsonString = await rootBundle.loadString('assets/locations.json');
  
  // 将JSON字符串解析为Map
  List<dynamic> jsonList = json.decode(jsonString);
  
  // 将Map转换为Location对象列表
  List<Location> locations = jsonList.map((json) => Location.fromJson(json)).toList();
  
  return locations;
}

GoogleMap(
  markers: Set<Marker>.from(locations.map((location) => Marker(
    markerId: MarkerId(location.latitude.toString() + location.longitude.toString()),
    position: LatLng(location.latitude, location.longitude),
    // 添加其他标记属性
  ))),
  // 添加其他GoogleMap属性
)