func ValidateMaxServerConnectionAge(in time.Duration) error {
	if err := IsNegativeDuration(in); err != nil {
		return fmt.Errorf("%v: --keepaliveMaxServerConnectionAge only accepts positive duration eg: 30m", err)
	}
	return nil
}

// IsNegativeDuration check if the duration is negative
func IsNegativeDuration(in time.Duration) error {
	if in < 0 {
		return fmt.Errorf("invalid duration: %s", in.String())