// DialTimeout optionally specifies a dial timeout.
	// If zero, a default is used.
	// If negative, the timeout is disabled.
	DialTimeout time.Duration

func (dp *DialProxy) HandleConn(src net.Conn) {
	ctx := context.Background()
	var cancel context.CancelFunc
	if dp.DialTimeout >= 0 {
		ctx, cancel = context.WithTimeout(ctx, dp.dialTimeout())
	}
	dst, err := dp.dialContext()(ctx, "tcp", dp.Addr)