func randomString(n int, alphabet string) string {
	r := timeSeed()
	b := make([]byte, n)
	for i := range b {
		b[i] = alphabet[r.Intn(len(alphabet))]
	}
	return string(b)
}
func randomString(n int, alphabet string) string {
	r := timeSeed()
	b := make([]byte, n)
	for i := range b {
		b[i] = alphabet[r.Intn(len(alphabet))]
	}
	return string(b)
}
// randomString generates a random string of given length using specified alphabet.