code: func (c *LRU) Get(base int64) bgzf.Block {
  	c.mu.Lock()
  	defer c.mu.Unlock()
  
  	n, ok := c.table[base]
  	if !ok {
  		return nil
  	}
  	remove(n, c.table)
  	return n.b
  }
docs: // Get returns the Block in the Cache with the specified base or a nil Block
  // if it does not exist.