code: func (h *Handler) GetOfferingIncome(
  	tkn, offeringID string) (*uint, error) {
  	logger := h.logger.Add("method", "GetOfferingIncome",
  		"offeringID", offeringID)
  
  	return h.uintFromQuery(logger, tkn,
  		`SELECT SUM(channels.receipt_balance)
  		     FROM channels
  		   WHERE channels.offering=$1`, offeringID)
  }
docs: // GetOfferingIncome returns total receipt balance from all channels of
  // offering with given id.