我不确定你的具体目标，但如果你只想定制gRPC网关，你可以按照这种方法。或者，你可以将逻辑转移到一个单独的函数。

// run starts the HTTP server and sets up a custom gRPC-gateway route.
// It registers the gRPC server endpoint and a custom POST route ("/auth").
func run() error {
    // Create a background context and cancel function for graceful shutdown
    ctx := context.Background()
    ctx, cancel := context.WithCancel(ctx)
    defer cancel()

    // Create a gRPC-gateway multiplexer
    mux := runtime.NewServeMux()

    // Register gRPC server endpoint with insecure transport credentials
    opts := []grpc.DialOption{grpc.WithTransportCredentials(insecure.NewCredentials())}
    err := gw.RegisterYourServiceHandlerFromEndpoint(ctx, mux, *grpcServerEndpoint, opts)
    if err != nil {
        return err
    }

    // Handle custom POST route ("/auth")
    err = mux.HandlePath("POST", "/auth", func(w http.ResponseWriter, r *http.Request, pathParams map[string]string) {
        // Create a map with the desired data
        responseData := map[string]string{
            "data": "something",
        }

        // Convert the map to a JSON string
        resp, err := json.Marshal(responseData)
        if err != nil {
            http.Error(w, "Error encoding JSON", http.StatusInternalServerError)
            return
        }

        // Set the Content-Type header to application/json
        w.Header().Set("Content-Type", "application/json")

        // Write the JSON response to the response writer
        w.Write(resp)
    })

    if err != nil {
        return err
    }

    // Start HTTP server (and proxy calls to gRPC server endpoint)
    return http.ListenAndServe(":8081", mux)
}

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