postBody method
Returns the body of the given uri
after a POST request. This process
is async, thus the body is returned as a future String instance.
Implementation
Future<String> postBody(Uri uri, {Map<String, String>? headers}) async {
final res = await postResponse(uri, headers: headers);
if (isErrorCode(res.statusCode)) {
throw SessionInvalidException(res.statusCode);
}
return res.body;
}