contrib/recipes/barrier.go
func (b *Barrier) Hold() error {
	_, err := newKey(b.client, b.key, v3.NoLease)
	return err
}
func (b *Barrier) Hold() error {
	_, err := newKey(b.client, b.key, v3.NoLease)
	return err
}
// Hold creates the barrier key causing processes to block on Wait.