pubsub example does not work

[yyzcode]

func (s *Sub) Process(ctx context.Context, event *proto.Event) error {
	md, _ := metadata.FromContext(ctx)
	log.Logf("[pubsub.1] Received event %+v with metadata %+v\n", event, md)
	// do something with event
	return nil
}

// Alternatively a function can be used
func subEv(ctx context.Context, event *proto.Event) error {
	md, _ := metadata.FromContext(ctx)
	log.Logf("[pubsub.2] Received event %+v with metadata %+v\n", event, md)
	// do something with event
	return nil
}

in this demo, the handler function of subscribe topic used a pointer parameter, it will cause an panic error: "file=server/rpc_router.go:512 level=error panic recovered: reflect.Value.Addr of unaddressable value".

I tried use value parameter to fix and it works.