code: func (s *Slot) finishFetch(completed bool, result interface{}, exp time.Time) {
  	s.lock.Lock()
  	defer s.lock.Unlock()
  	s.fetching = false
  	if completed {
  		s.current = result
  		s.exp = exp
  	}
  }
docs: // finishFetch switches the Slot back to "not fetching" state, remembering the
  // fetched value.
  //
  // 'completed' is false if the fetch panicked.