code: func (w *Worker) DecrementCurrentSupply(job *data.Job) error {
  	logger := w.logger.Add("method", "DecrementCurrentSupply", "job", job)
  	offering, err := w.relatedOffering(logger, job, data.JobDecrementCurrentSupply)
  	if err != nil {
  		return err
  	}
  
  	offering.CurrentSupply--
  
  	err = data.Save(w.db.Querier, offering)
  	if err != nil {
  		logger.Error(err.Error())
  		return ErrInternal
  	}
  
  	return nil
  }
docs: // DecrementCurrentSupply finds offering and decrements its current supply.