main.dart

import 'dart:async';
import 'dart:convert';

void main() {
  Future<String> queryOne() async {
    return "[1,2,3]";
  }

  Future<String> queryTwo() async {
    return "{\"test\":true}";
  }

  T parseJson<T>(String resp) {
    const json = const JsonCodec();

    try {
      return json.decode(resp);
    } catch (e) {
      print('Some error on parsing json: $e');
      return null;
    }

    print('Invalid resp: $resp');
    return null;
  }

  queryOne().then(parseJson).then((Map<String, dynamic> onValue) {
    return 1;
  });

  for (int i = 0; i < 5; i++) {
    print('hello ${i + 1}');
  }
}