log DoH HTTP server error logs in CoreDNS format (#5457)

Signed-off-by: Ondřej Benkovský <ondrej.benkovsky@jamf.com>

core/dnsserver/server_https.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/tls"
 	"fmt"
+	stdlog "log"
 	"net"
 	"net/http"
 	"strconv"
@@ -13,6 +14,7 @@ import (
 	"github.com/coredns/coredns/plugin/metrics/vars"
 	"github.com/coredns/coredns/plugin/pkg/dnsutil"
 	"github.com/coredns/coredns/plugin/pkg/doh"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/plugin/pkg/response"
 	"github.com/coredns/coredns/plugin/pkg/reuseport"
 	"github.com/coredns/coredns/plugin/pkg/transport"
@@ -27,6 +29,15 @@ type ServerHTTPS struct {
 	validRequest func(*http.Request) bool
 }
 
+// loggerAdapter is a simple adapter around CoreDNS logger made to implement io.Writer in order to log errors from HTTP server
+type loggerAdapter struct {
+}
+
+func (l *loggerAdapter) Write(p []byte) (n int, err error) {
+	clog.Debug(string(p))
+	return len(p), nil
+}
+
 // HTTPRequestKey is the context key for the current processed HTTP request (if current processed request was done over DOH)
 type HTTPRequestKey struct{}
 
@@ -63,6 +74,7 @@ func NewServerHTTPS(addr string, group []*Config) (*ServerHTTPS, error) {
 		ReadTimeout:  5 * time.Second,
 		WriteTimeout: 10 * time.Second,
 		IdleTimeout:  120 * time.Second,
+		ErrorLog:     stdlog.New(&loggerAdapter{}, "", 0),
 	}
 	sh := &ServerHTTPS{
 		Server: s, tlsConfig: tlsConfig, httpsServer: srv, validRequest: validator,