String validasiEmail(String value) {
    Pattern pattern =
        r'^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$';
    RegExp regex = new RegExp(pattern);
    if (!regex.hasMatch(value))
      return 'Enter Valid Email';
    else
      return null;
  }