main function
void
main()
Implementation
void main() async {
List<PointField> pointFields = [];
final jsonData = await File('./point.json').readAsString().then((fileContents) => json.decode(fileContents));
for (var elem in jsonData) {
pointFields.add(PointField.fromJson(Map<String, dynamic>.from(elem)));
}
print(pointFields);
}