code: func (s *BulkProcessorService) FlushInterval(interval time.Duration) *BulkProcessorService {
  	s.flushInterval = interval
  	return s
  }
docs: // FlushInterval specifies when to flush at the end of the given interval.
  // This is disabled by default. If you want the bulk processor to
  // operate completely asynchronously, set both BulkActions and BulkSize to
  // -1 and set the FlushInterval to a meaningful interval.