code: func (g *GRPCServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
  	// magic combo match signifying GRPC request
  	// https://grpc.io/blog/coreos
  	if r.ProtoMajor == 2 && strings.Contains(r.Header.Get("Content-Type"), "application/grpc") {
  		g.grpcHandler.ServeHTTP(w, r)
  	} else {
  		g.httpHandler.ServeHTTP(w, r)
  	}
  }
docs: // ServeHTTP dispatches requests based on the request type