gRPC-Go: protoc-gen-go-grpc changes

[Doug Fawley]

If you don't use gRPC-Go or protobuf, you can stop reading now.

As you may be aware, the protobuf module at github.com/golang/protobuf has been superseded by google.golang.org/protobuf.  In combination with this change, the new module will not provide any gRPC codegen capabilities; those are being transitioned to google.golang.org/grpc/cmd/protoc-gen-go-grpc.

We are using this opportunity to correct a long-standing issue with the generated code for gRPC-Go: adding new methods to a service should be a backward-compatible change.  Unfortunately, this will require some minor changes to application code.  However, we believe this is worth the benefit, and provides some additional flexibility not previously possible.

The proposed API for the new version of the codegen tool is now ready for testing.  It is still v0, meaning API changes are still possible.  You can find the details in the tool's README.  For discussions about the API, you are welcome to follow-up either here or in the issue tracking these changes.

Thanks,

Doug