code: func Logger() Handler {
  	return func(res http.ResponseWriter, req *http.Request, c Context, log *log.Logger) {
  		start := time.Now()
  
  		addr := req.Header.Get("X-Real-IP")
  		if addr == "" {
  			addr = req.Header.Get("X-Forwarded-For")
  			if addr == "" {
  				addr = req.RemoteAddr
  			}
  		}
  
  		log.Printf("Started %s %s for %s", req.Method, req.URL.Path, addr)
  
  		rw := res.(ResponseWriter)
  		c.Next()
  
  		log.Printf("Completed %v %s in %v\n", rw.Status(), http.StatusText(rw.Status()), time.Since(start))
  	}
  }
docs: // Logger returns a middleware handler that logs the request as it goes in and the response as it goes out.