}

  public static void main(String... args) throws Exception {
    new UploadProgress().run();
  }

  private static class ProgressRequestBody extends RequestBody {

    private final ProgressListener progressListener;
    private final RequestBody delegate;

    public ProgressRequestBody(RequestBody delegate, ProgressListener progressListener) {
      this.delegate = delegate;
      this.progressListener = progressListener;

              .post(ProgressRequestBody(requestBody, progressListener)).build()

          client.newCall(request).execute().use { response ->
            if (!response.isSuccessful) throw IOException("Unexpected code $response")
            println(response.body.string())
          }
        }

        private class ProgressRequestBody(