func (pool *ReaderPool) Len() int {
	pool.mu.Lock()
	defer pool.mu.Unlock()
	return len(pool.givenOut)
}
func (pool *ReaderPool) Len() int {
	pool.mu.Lock()
	defer pool.mu.Unlock()
	return len(pool.givenOut)
}
func ( pool * ReaderPool ) Len ( ) int { pool . mu . Lock ( ) defer pool . mu . Unlock ( ) return len ( pool . givenOut ) }
// Len is the number of currently given out throttled readers.
Len is the number of currently given out throttled readers .