code: func parseCronSchedule(expr string, randSeed uint64) (*Schedule, error) {
  	cronexprLock.Lock()
  	exp, err := cronexpr.Parse(expr)
  	cronexprLock.Unlock()
  	if err != nil {
  		return nil, err
  	}
  	return &Schedule{cronExpr: exp}, nil
  }
docs: // parseCronSchedule parses crontab-like schedule string.