code: func (w *Worker) checkInPeriod(logger log.Logger, hash common.Hash,
  	periodKey string, periodErr error) error {
  	updateBlockNumber, err := w.getOfferingBlockNumber(logger, hash)
  	if err != nil {
  		return err
  	}
  
  	lastBlock, err := w.ethBack.LatestBlockNumber(context.Background())
  	if err != nil {
  		logger.Error(err.Error())
  		return ErrInternal
  	}
  
  	removePeriod, err := data.ReadUintSetting(w.db.Querier, periodKey)
  	if err != nil {
  		return periodErr
  	}
  
  	if uint64(updateBlockNumber)+uint64(removePeriod) > lastBlock.Uint64() {
  		return periodErr
  	}
  
  	return nil
  }
docs: // checkInPeriod checks an offering being in period specified by periodKey.