grpc extension is not working

[SButterfly]

Proposal

I wanted to use wiremock grpc for my project, but it wasn't working.

proto contained of multiple files:
myservice.proto

syntax = "proto3";
package wallet.myservice;

import "wallet/errors.proto";

service MyService {
  rpc QueryEvents(QueryEventsRequest) returns (QueryEventsResponse) {}
}

message LogTruncated {}

message Error {
  oneof error {
    errors.OtherError other_error = 1;
    LogTruncated log_truncated = 2;
  }
}

message QueryEventsRequest {
  uint64 from = 1;
  uint64 to = 2;
}

message QueryEventsResponse {
  Error error = 1;

  uint64 from = 2;
  uint64 to = 3;

  repeated Event event = 4;
}
message Event {
  EventPayload payload = 2;
}

message EventPayload {
}

errors.proto

syntax = "proto3";
package wallet.errors;

message OtherError {
  string reason = 1;
}

mappings.json

{
    "request": {
        "method": "POST",
        "urlPath": "/wallet.myservice.MyService/QueryEvents"
    },

    "response": {
        "status": 200,
        "body": "{\"from\": 0, \"to\": 0}",
        "transformers": ["response-template"],
        "headers" : {
            "grpc-status-name" : "OK"
        }
    }
}

And run command

protoc \
  --descriptor_set_out wiremock-data/grpc/services.dsc \
  --proto_path proto_files \
  proto_files/wallet/myservice.proto

docker run -it --rm \
  -p 8080:8080 \
  --name wiremock \
  -v $PWD/wiremock-data:/home/wiremock \
  -v $PWD/extensions:/var/wiremock/extensions \
  wiremock/wiremock:3.9.1

Reproduction steps

I have created a sample project to reproduce the problem:
https://github.com/SButterfly/grpc-wiremock-bug

References

No response