code: func (hec *Client) WaitForAcknowledgement() error {
  	ctx, cancel := context.WithTimeout(context.Background(), defaultAcknowledgementTimeout)
  	defer cancel()
  	return hec.WaitForAcknowledgementWithContext(ctx)
  }
docs: // WaitForAcknowledgement blocks until the Splunk indexer has acknowledged
  // that all previously submitted data has been successfully indexed or if the
  // default acknowledgement timeout is reached. This requires the HEC token
  // configuration in Splunk to have indexer acknowledgement enabled.