Update to use the latest protobuf package to build pb (coredns#5193)

* Update to use the latest protobuf package to build pb

The pb package was generated some time ago with old version
of https://github.com/golang/protobuf which was deprecated
and in favor of google.golang.org/protobuf (see
deprecation notice in https://pkg.go.dev/github.com/golang/protobuf)

This PR updates the generation of pb package with
v1.27.1 of google.golang.org/protobuf.

Signed-off-by: Yong Tang <[email protected]>

* Exclude pb from import test

Signed-off-by: Yong Tang <[email protected]>

core/dnsserver/server_grpc.go

@@ -22,6 +22,7 @@ import (
 // ServergRPC represents an instance of a DNS-over-gRPC server.
 type ServergRPC struct {
 	*Server
+	*pb.UnimplementedDnsServiceServer
 	grpcServer *grpc.Server
 	listenAddr net.Addr
 	tlsConfig  *tls.Config

pb/Makefile

@@ -2,11 +2,18 @@
 # from: https://github.com/golang/protobuf to make this work.
 # The generate dns.pb.go is checked into git, so for normal builds we don't need
 # to run this generation step.
+# Note: The following has been used when regenerate pb:
+#  curl -OL https://github.com/protocolbuffers/protobuf/releases/download/v3.19.4/protoc-3.19.4-linux-x86_64.zip
+#  go install google.golang.org/protobuf/cmd/[email protected]
+#  go install google.golang.org/grpc/cmd/[email protected]
+#  export PATH="$PATH:$(go env GOPATH)/bin"
+#  rm pb/dns.pb.go pb/dns_grpc.pb.go
+#  make pb
 
 all: dns.pb.go
 
 dns.pb.go: dns.proto
-	protoc --go_out=plugins=grpc:. dns.proto
+	protoc --go_out=. --go-grpc_out=. dns.proto
 
 .PHONY: clean
 clean:

pb/dns.proto

@@ -1,7 +1,7 @@
 syntax = "proto3";
 
 package coredns.dns;
-option go_package = "pb";
+option go_package = ".;pb";
 
 message DnsPacket {
 	bytes msg = 1;