code: func NewRandom(n int) Cache {
  	if n < 1 {
  		return nil
  	}
  	return &Random{
  		table: make(map[int64]bgzf.Block, n),
  		cap:   n,
  	}
  }
docs: // NewRandom returns a random eviction cache with n slots. If n is less than 1
  // a nil cache is returned.