httprouter forward to another handler with parameters & url update

Question

I'm thinking about the following scenario:

Suppose I want have handler X in which I have made some calculations but now want to forward to another handler Y before returning the request.

It would be something like

func X(w http.ResponseWriter, r *http.Request, params httprouter.Params){
    //calculations
    if condition{
        var fp httprouter.Params
        fp = append(fp, httprouter.Param{Key: "KEY", Value: "VALUE"})
        w.WriteHeader(301)
        Y(w, r, fp)
        return
    }
}

The problem I have is that while the page loads and it has a 301 header the redirect is not registered. It's like a 200 page with a 301.

I know there's http.Redirect, but it doesn't forward the parameters that could be helpful. Is there an easy solution to this?

Answer 1

"If WriteHeader has not yet been called, Write calls WriteHeader(http.StatusOK) before writing the data." (From http.Server documentation)

Make sure you don't write any bytes to the ResponseWriter if you think you will redirect. You can user a buffer or something instead of writing directly to the w

As far as getting your first function's parameters into your second function... You could use cookies, or easier. The redirect path could include the parameters. Either as path or GET variables. Here's an example with path using that httprouter package you are already using.

In X(),

    if weAreRedirecting {
        http.Redirect(w, r, "/y/"+params.ByName("key"), http.StatusFound)
        return
    }

And in your router, router.GET("/y/:key", Y)