Unknown gRPC error with no error message - gRPC-web and goproxy - flutter-web

Question

I'm trying to build a web application with the following stack:
Flutter/Dart
Go/goproxy
gRPC
MongoDB
I was able to successfully define and compile a protobuf into Dart and Go, however now that I'm trying to integrate the UI with the backend, I am running into the following issue:
Error: gRPC Error (code: 2, codeName: UNKNOWN, message:
null, details: [], rawResponse: null, trailers: {})
Here is my client code:
import 'package:grpc/grpc_web.dart';
import 'package:proj/protos/cards.pb.dart';
import 'package:proj/protos/cards.pbgrpc.dart';
class FiltersService {
static ResponseFuture<Filters> getFilters() {
GrpcWebClientChannel channel =
GrpcWebClientChannel.xhr(Uri.parse('http://localhost:9000'));
FiltersServiceClient clientStub = FiltersServiceClient(
channel,
);
return clientStub.getFilters(Void());
}
}
The server controller code:
const (
port = 9000
)
var (
grpcServer *grpc.Server
)
func StartServer() {
log.Println("Starting server")
listener, err := net.Listen("tcp", fmt.Sprintf(":%v", port))
if err != nil {
log.Fatalf("Unable to listen to port %v\n%v\n", port, err)
}
repositories.ConnectToMongoDB()
grpcServer = grpc.NewServer()
registerServices()
grpcWebServer := grpcweb.WrapServer(grpcServer)
httpServer := &http.Server{
Handler: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.ProtoMajor == 2 {
grpcWebServer.ServeHTTP(w, r)
} else {
w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Access-Control-Allow-Methods", "POST, GET, OPTIONS, PUT, DELETE")
w.Header().Set("Access-Control-Allow-Headers", "Accept, Content-Type, Content-Length, Accept-Encoding, X-CSRF-Token, Authorization, X-User-Agent, X-Grpc-Web")
w.Header().Set("grpc-status", "")
w.Header().Set("grpc-message", "")
if grpcWebServer.IsGrpcWebRequest(r) {
grpcWebServer.ServeHTTP(w, r)
}
}
}),
}
httpServer.Serve(listener)
}
// Register services defined in protobufs to call from UI
func registerServices() {
cardsService := &services.CardsService{}
protos.RegisterCardsServiceServer(grpcServer, cardsService)
filtersService := &services.FiltersService{}
protos.RegisterFiltersServiceServer(grpcServer, filtersService)
}
I can tell that the server is receiving the request properly, and when I output the response of the service, I am getting the expected response.
Here is the service I am calling:
func (service *FiltersService) GetFilters(ctx context.Context, void *protos.Void) (*protos.Filters, error) {
filters := repositories.GetFilters()
return converters.FiltersStructToFiltersProtoConverter(filters), nil
}
When I output the response of converters.FiltersStructToFiltersProtoConverter(filters), I get the correct output, so it looks like there's still an issue with the way my server is set up.
I know this isn't a lot of info to go on, however I'm not sure what other information you may need, but can add as needed.