limit

type Limiter interface {
	// returns how many holder are running
	// return -1 if u donot want to implement this
	Running() int

	// Acquire by this keys, returns error if no available resource
	// Panic if key is unhashable type necessarily
	Acquire(keys ...interface{}) error

	// Release this keys holder
	// Panic if not acquire yet necessarily
	// Panic if key is unhashable type necessarily
	Release(keys ...interface{})
}

type ResettableLimiter interface {
	Limiter

	// Reset the available resource
	Reset(n int)
}