lease/lessor.go
func (le *lessor) Attach(id LeaseID, items []LeaseItem) error {
	le.mu.Lock()
	defer le.mu.Unlock()

	l := le.leaseMap[id]
	if l == nil {
		return ErrLeaseNotFound
	}

	l.mu.Lock()
	for _, it := range items {
		l.itemSet[it] = struct{}{}
		le.itemMap[it] = id
	}
	l.mu.Unlock()
	return nil
}
func (le *lessor) Attach(id LeaseID, items []LeaseItem) error {
	le.mu.Lock()
	defer le.mu.Unlock()

	l := le.leaseMap[id]
	if l == nil {
		return ErrLeaseNotFound
	}

	l.mu.Lock()
	for _, it := range items {
		l.itemSet[it] = struct{}{}
		le.itemMap[it] = id
	}
	l.mu.Unlock()
	return nil
}
// Attach attaches items to the lease with given ID. When the lease
// expires, the attached items will be automatically removed.
// If the given lease does not exist, an error will be returned.