Hi OP, I don't know if it helps with your issues, but some years ago I wrote an article precisely about using protobuf between Dart and Go and it included a sec

Hi OP, I don't know if it helps with your issues, but some years ago I wrote an article precisely about using protobuf between Dart and Go and it included a section on async: https://tech.craveiro.pt/go-for-dart-with-protocol-buffers https://tech.craveiro.pt/go-for-dart-with-protocol-buffers.