Flutter export pdf from JSON

My data from JSON gives an error when fetching, and it does not display when exported to pdf, any suggestions how to fix this? Thank you.

class User {
  final int id;
  final String name;
  final String position;
 
  User(
      {this.id,
      this.name, 
      this.position,
      });

  factory User.fromMap(Map<String, dynamic> json) => User(
        id: json["id"],
        name: json["name"],
        position: json["position"],
      );
}

class PdfApi {
  static Future<File> generateTable() async {
    var url = Uri.parse('https:....');
    var response = await http.get(url);
    final jsonData = json.decode(response.body);

    final pdf = Document();
    final headers = [
      'id',
      'name',
      'position',
    ];
 
    final data = jsonData.map<User>((json) => User.fromMap(json)).toList();
  }
}