FetchUrl constructor
      
      FetchUrl({ 
    
- required String url,
- required String saveToPath,
- Map<String, String> ? headers,
- FetchMethod method = FetchMethod.get,
- OnFetchProgress progress = _devNull,
- FetchData? data,
ctor.
Implementation
FetchUrl(
    {required this.url,
    required this.saveToPath,
    Map<String, String>? headers,
    this.method = FetchMethod.get,
    this.progress = _devNull,
    this.data}) {
  this.headers = headers ?? <String, String>{};
  if (data != null && method != FetchMethod.post) {
    throw FetchException('FetchData is not supported for the FetchMethod:'
        '${EnumHelper().getName(method)}');
  }
}