Future<String> fetchUrl(String url, { Map<String, String> headers })

Fetches the specified url from HTTP. If headers is specified, the headers will be added onto the request.

Source 

static Future<String> fetchUrl(String url, {Map<String, String> headers}) async {
  var request = await createRequest("GET", url, headers: headers);
  var response = await request.close();
  return const Utf8Decoder().convert(await readBytesFromResponse(response));
}