const (
    TokenLens int = 16
)
func GenerateTokens() string {
    rand.Seed(time.Now().UnixNano())
    runes := []rune("abcdefghijklmnopqrstuvwxyz0123456789")
    byteToken := make([]rune, TokenLens)
    for i := range byteToken {
        byteToken[i] = runes[rand.Intn(len(runes))]
    }
    return string(byteToken)
}