Avoid copying dns.Msg structs containing atomic.Bool

Fixes go vet warning

Fixes #3073

Author: jedisct1

dnscrypt-proxy/plugin_cache.go

@@ -15,7 +15,7 @@ const StaleResponseTTL = 30 * time.Second
 
 type CachedResponse struct {
 	expiration time.Time
-	msg        dns.Msg
+	msg        *dns.Msg
 }
 
 type CachedResponses struct {
@@ -141,7 +141,7 @@ func (plugin *PluginCacheResponse) Eval(pluginsState *PluginsState, msg *dns.Msg
 	)
 	cachedResponse := CachedResponse{
 		expiration: time.Now().Add(ttl),
-		msg:        *msg,
+		msg:        msg.Copy(),
 	}
 	var cacheInitError error
 	cachedResponses.cacheOnce.Do(func() {

dnscrypt-proxy/serversInfo.go

@@ -761,7 +761,7 @@ func fetchDNSCryptServerInfo(proxy *Proxy, name string, stamp stamps.ServerStamp
 		msg, _, _, err := DNSExchange(
 			proxy,
 			proxy.xTransport.mainProto,
-			&query,
+			query,
 			stamp.ServerAddrStr,
 			dnscryptRelay,
 			&name,
@@ -849,7 +849,7 @@ func dohNXTestPacket(msgID uint16) []byte {
 	return msg.Data
 }
 
-func plainNXTestPacket(msgID uint16) dns.Msg {
+func plainNXTestPacket(msgID uint16) *dns.Msg {
 	qName := make([]byte, 16)
 	charset := "abcdefghijklmnopqrstuvwxyz"
 	for i := range qName {
@@ -858,7 +858,7 @@ func plainNXTestPacket(msgID uint16) dns.Msg {
 	msg := dns.NewMsg(string(qName)+".test.dnscrypt.", dns.TypeNS)
 	msg.ID = msgID
 	msg.RecursionDesired = true
-	return *msg
+	return msg
 }
 
 func fetchDoHServerInfo(proxy *Proxy, name string, stamp stamps.ServerStamp, isNew bool) (ServerInfo, error) {