// h2preload adds HTTP/2 preload header configured in h2config.
func h2preload(h http.Header, host, tplname string) {
a, ok := h2config[tplname]
if !ok {
return
}
s := "https"
if isDevServer() {
s = "http"
}
http2preload.AddHeader(h, s, path.Join(host, config.Prefix), a)
}
// handleGopher demonstrates how to push resources
// without a manifest file.
func handleGopher(w http.ResponseWriter, r *http.Request) {
assets := map[string]http2preload.AssetOpt{
gopher: {Type: http2preload.Image},
}
s := "http"
if r.TLS != nil {
s = "https"
}
// the next line will add the following header:
// Link: <host/gopher.png>; rel=preload; as=image
http2preload.AddHeader(w.Header(), s, r.Host, assets)
// respond with minimal HTML5, omitting <html> and <body>
fmt.Fprintf(w, `<img src="%s">`, gopher)
}