code: func (db *Database) buildReturning() string {
  	var query bytes.Buffer
  	query.WriteString(" RETURNING ")
  	query.WriteString(strings.Join(getSQLFields(db.models[0]), ","))
  	return query.String()
  }
docs: // buildReturning returns the RETURNING part of the query
  // it explicits every fields in the current model.
  // In that way we're able to easily Scan the results