code: func Interval(db XODB, v0 pgtypes.Reltime, v1 time.Time, v2 *time.Duration, v3 int) (*time.Duration, error) {
  	var err error
  
  	// sql query
  	const sqlstr = `SELECT pg_catalog.interval($1, $2, $3, $4)`
  
  	// run query
  	var ret *time.Duration
  	XOLog(sqlstr, v0, v1, v2, v3)
  	err = db.QueryRow(sqlstr, v0, v1, v2, v3).Scan(&ret)
  	if err != nil {
  		return nil, err
  	}
  
  	return ret, nil
  }
docs: // Interval calls the stored procedure 'pg_catalog.interval(reltime, time without time zone, interval, integer) interval' on db.