code: func (l *blocksLRU) get(offset int64) (b block, ok bool) {
  	elem, ok := l.blocks[offset]
  	if !ok {
  		return block{}, false
  	}
  	l.ll.MoveToFront(elem)
  	return elem.Value.(block), true
  }
docs: // get returns (block, true) if it's in the cache or (block{}, false) otherwise.