code: func itemLock() []byte {
  	b := make([]byte, 4)
  	binary.LittleEndian.PutUint32(b, rand.Uint32())
  	return b
  }
docs: // itemLock creates a pseudorandom memcache lock value that enables each call of
  // Get/GetMulti to determine if a lock retrieved from memcache is the one it
  // created. This is only important when multiple calls of Get/GetMulti are
  // performed concurrently for the same previously uncached entity.