code: func (s *State) Release() {
  	s.dbCond.L.Lock()
  	defer s.dbCond.L.Unlock()
  	s.dbUsers--
  	if s.dbUsers == 0 {
  		s.dbCond.Broadcast()
  	}
  }
docs: // Release releases the state by decrementing s.dbUsers, broadcasting the
  // condition variable if no users are left to wake CloseDB.