No proxy is required if you only write servers in go with their connect-go library. Packing protos is not glamorous work, but I'm not willing to adopt a gRPC protocol that limits implementation choices.

If you have gRPC services chances are you already have a L7 reverse-proxy like envoy running with grpc/grpc-web support whether doing it yourself, or as part of your cloud provider. So IMO their connect-go library is only useful if you directly expose the server on the internet, and only use the go programming language.