Posted this on the blog as well, but some here might find it useful.

Instead of duplicating code to implement common/middleware functionality, I like to just pass around functions. I usually just have one makeStandardHandler type function that covers most cases. For the special cases, I can easily combine middleware in any order for the desired result.

  // Execution timing middleware
  func makeTimingHandler(fn func(http.ResponseWriter, *http.Request)) http.HandlerFunc {
  	return func(w http.ResponseWriter, r *http.Request) {
  		requestStartTime := time.Now()
  		fn(w, r)
  		totalRequestTime := time.Now().Sub(requestStartTime)
  		log.Printf("URL: %s TIME: %s", r.URL.Path, totalRequestTime.String())
  	}
  }
  
  // Serve up one file
  func makeSingleFileHandler(file string) http.HandlerFunc {
  	return func(w http.ResponseWriter, r *http.Request) {
  		http.ServeFile(w, r, file)
  	}
  }
  
  func main() {
  	...
  	http.HandleFunc("/robots.txt", makeTimingHandler(makeSingleFileHandler("./s/robots.txt")))
  	http.HandleFunc("/", makeTimingHandler(indexHandler))
  	...
  }