Factory null safety

class Process {
  static late Process _instance;

  Process._internal() {
    _instance = this;
  }

  factory Process() => _instance ?? Process._internal();

  static bool processing = true;
  static late bool finishedSuccessfully;
  static bool? isDioError;
  static int statusCode = 0;
  static late String resultMessage;
  static String friendlyMessage = 'Ocorreu um erro, favor tentar novamente.';
  static late String httpHeader;
  static late String httpData;
  static late String resultException;
  static late String request;