GZip encoding for GO V1 using custom responsewriter

gistfile1.go

package main

import (
	"compress/gzip"
	"io"
	"net/http"
	"strings"
)

type gzipResponseWriter struct {
	io.Writer
	http.ResponseWriter
}

func (w gzipResponseWriter) Write(b []byte) (int, error) {
	return w.Writer.Write(b)
}

func makeGzipHandler(fn http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if !strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
			fn(w, r)
			return
		}
		w.Header().Set("Content-Encoding", "gzip")
		gz := gzip.NewWriter(w)
		defer gz.Close()
		gzr := gzipResponseWriter{Writer: gz, ResponseWriter: w}
		fn(gzr, r)
	}
}

func handler(w http.ResponseWriter, r *http.Request) {

	w.Header().Set("Content-Type", "text/plain")
	w.Write([]byte("This is a test."))
}

func main() {
	http.ListenAndServe(":1113", makeGzipHandler(handler))
}

Since a stackoverflow article links here and likey gets some traffic, I figured I would warn people that the .Close on the gzip writer writes some kind of footer, and if the response from the handler needs to be a 304 or 204 etc then that will break.
As far as I can see in the spec http://www.w3.org/Protocols/rfc2616/rfc2616-sec7.html#sec7 its ok to leave the Content-Encoding header in the response but there should not be any body.

Also, the error from gz.Close() isn't being checked, which leads to mysterious failures like golang/go#14975 (comment). If you use this, make sure to check that error.

A added a new commit to my fork that fixes some issues: https://gist.github.com/erikdubbelboer/7df2b2b9f34f9f839a84

The issue from @optimality about not handling gz.Close errors still stands as everyone should handle this in their own way since http.HandlerFunc can't return errors.

License?