Hey, I've made a small tool that can be useful for some.
https://github.com/utrack/clayClay is a generator/platform that enables you to serve your gRPC services via HTTP handlers for testing purposes. Swagger definitions are generated as well, thanks to protoc-gen-swagger.
Unlike grpc-gateway, you don't need an intermediate instance to act as a gateway - http is served by instance itself instead.
It uses code generation via protoc plugin `protoc-gen-goclay`.
While example code is very simple - the API is easily extendable, allowing you to swap any part of a server, or use your own server implementation entirely.