How to serve two static sites with gin in golang?

I want to create an application that will call a boolean function and depending on the result provide 1 of 2 compiled react apps as static sites.

I'm using the LoadHTMLGlob function recommended by gin and it works fine with .tmpl files like the example in thier docs. However when doing just static html with a static directory for each site nothing seems to go well.

File Structure:

├── main.go
└── sites
    ├── new
    │   ├── index.html
    │   └── static
    └── old
        ├── index.html
        └── static

Go Code:

func main() {
    r := gin.Default()
    //r.LoadHTMLFiles("sites/old/index.html", "sites/new/index.html") //doesn't complain, but can't load html
    r.LoadHTMLGlob("sites/**/*") // complains about /static being a dir on boot
    r.GET("/sites/lib", func(c *gin.Context) {
        id := c.Query("id")
        useNewSite, err := isBetaUser(id)
        if err != nil {
            c.AbortWithStatusJSON(500, err.Error())
            return
        }
        if useNewSite {
            c.HTML(http.StatusOK, "new/index.html", nil)
        } else {
            c.HTML(http.StatusOK, "old/index.html", nil)
        }
    })
    routerErr := r.Run(":8080")
    if routerErr != nil {
        panic(routerErr.Error())
    }
}

I expect that when isBetaUser comes back as true it should load the static content under sites/new otherwise load sites/old.

However loading globs produces: panic: read sites/new/static: is a directory when starting panics.

Loading the html files individually (commented out above) Runs fine, but when a request comes it panics with:

html/template: "new/index.html" is undefined

I've also string using sites/[old||new]/index.html in c.HTML

Solution

Try sites/**/*.html to fix the panic.

And note that Go uses the template files' base name as the template name, so to execute a template you don't use "path/to/template.html" but "template.html". This, of course, causes a problem in your case since as explained in the documentation:

When parsing multiple files with the same name in different directories, the last one mentioned will be the one that results.

To fix this you need to explicitly name your templates which you can do by using the {{ define "template_name" }} action.

Open sites/new/index.html
Add {{ define "new/index.html" }} as the first line
Add {{ end }} as the last line
Repeat for sites/old/index.html with "old/index.html" as the name.