如何在Go中打开/保存文件在另一台计算机上？

I work on an web application written in Go and React. I am deploying that app on Google Cloud Platform, for which I chose the Compute Engine service.

I created 3 instances: an instance for running the Go part of the application, an other for the database server and the last for the React part. The OS of the three instances is Ubuntu 18.04.

I want my Go program to retrieve data from my database (that part works well) and serve them to the client (React) using websocket.

When I test my app locally, everything runs as expected but it's because html/css/js files are on the same computer that my Go files. But on GCE they are on two differents VMs. Actually this is how I serve a html file with Go:

indexFile, err := os.Open("views/index.html")
if err != nil {
    fmt.Println(err)
}
index, err := ioutil.ReadAll(indexFile)
if err != nil {
    fmt.Println(err)
}
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, string(index))
})
http.ListenAndServe(":8080", nil)

Does someone knows how I can make my app work with Go code on a VM and html/css/js on an other ?

Thanks :)