This API expresses exactly the intended result (either an error or data and response, never all or none) and allows them to be handled much more clearly.

Helper.swift

URLSession.shared.dataTask(with: url) { (result: Result<(response: URLResponse, data: Data), Error>) in // Type added for illustration purposes.
    switch result {
    case let .success(success):
        handleResponse(success.response, data: success.data)
    case let .error(error):
        handleError(error)
    }
}