static ssize_t defer_data_source_read_callback(nghttp2_session *session,
                                               int32_t stream_id, uint8_t *buf,
                                               size_t len, uint32_t *data_flags,
                                               nghttp2_data_source *source,
                                               void *user_data) {
  (void)session;
  (void)stream_id;
  (void)buf;
  (void)len;
  (void)data_flags;
  (void)source;
  (void)user_data;

  return NGHTTP2_ERR_DEFERRED;
}
static ssize_t defer_data_source_read_callback(nghttp2_session *session,
                                               int32_t stream_id, uint8_t *buf,
                                               size_t len, uint32_t *data_flags,
                                               nghttp2_data_source *source,
                                               void *user_data) {
  (void)session;
  (void)stream_id;
  (void)buf;
  (void)len;
  (void)data_flags;
  (void)source;
  (void)user_data;

  return NGHTTP2_ERR_DEFERRED;
}