Just a small note / Gist type of thing for today: I got tired of adding w.Header().Set("Access-Control-Allow-Origin", "*") to every handler function in my small Golang web app. I'm using Julien Schmidt's excellent httprouter module for simple routing. Turns out the Basic Authentication example is quite simple to adjust for a set-and-forget type of httprouter.Handle middleware:

// https://github.com/julienschmidt/httprouter middleware to set CORS header
func MiddleCORS(next httprouter.Handle) httprouter.Handle {
	return func(w http.ResponseWriter,
    r *http.Request, ps httprouter.Params) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		next(w, r, ps)
	}
}

Using the middleware is simple, just wrap your normal handler function:

router.GET("/someurl", MiddleCORS(SomeURLFunc))

Or both the middleware and the function it takes implement httprouter.Handle, you can just chain multiple middleware with MiddleCORS(AnotherMiddleware(SomeURLFunc)).