well known not encode as expected

[elvizlai]

For example

given proto def

rpc Version(google.protobuf.Empty) returns(google.protobuf.Struct);

with server response impl

	resp := &structpb.Struct{
		Fields: map[string]*structpb.Value{
			"proto_version": {Kind: &structpb.Value_StringValue{
				StringValue:  "aabbcc",
			}},
		},
	}

which expect:

{"proto_version":"aabbcc"}

but got:

{"fields":{"proto_version":{"string_value":"aabbcc"}}}

[ysugimoto]

Hi @elvizlai , sorry for being late reply.

I'm guessing we may not consider google's ptype so we need more improvement for that.
we'll investigate and may support, but I really appreciate it if you could do that and give a PR.