uuid v4 and func to swap in test

gistfile1.txt

var uuidFunc = uuidV4 // for swapping in test

func uuidV4() string {
	b := make([]byte, 16)
	_, err := io.ReadFull(rand.Reader, b)
	if err != nil {
		panic(err)
	}
	b[6] = (b[6] & 0x0F) | 0x40
	b[8] = (b[8] &^ 0x40) | 0x80
	return fmt.Sprintf("%x%x%x%x%x", b[:4], b[4:6], b[6:8], b[8:10], b[10:])
}