get method
Implementation
@override
Future<FileServiceResponse> get(String url,
    {Map<String, String>? headers}) async {
  final req = http.Request('GET', Uri.parse(url));
  if (headers != null) {
    req.headers.addAll(headers);
  }
  final httpResponse = await _httpClient.send(req);
  return HttpGetResponse(httpResponse);
}