fix: avoid modifying the request message id

dns/doh.go

@@ -109,6 +109,7 @@ func (doh *dnsOverHTTPS) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.
 	// formats that include the ID field from the DNS message header, such
 	// as "application/dns-message", SHOULD use a DNS ID of 0 in every DNS
 	// request.
+	m=m.Copy()
 	id := m.Id
 	m.Id = 0
 	defer func() {

dns/doq.go

@@ -89,6 +89,7 @@ func (doq *dnsOverQUIC) Address() string { return doq.addr }
 func (doq *dnsOverQUIC) ExchangeContext(ctx context.Context, m *D.Msg) (msg *D.Msg, err error) {
 	// When sending queries over a QUIC connection, the DNS Message ID MUST be
 	// set to zero.
+	m = m.Copy()
 	id := m.Id
 	m.Id = 0
 	defer func() {