code: func (g DebugHandler) Append(router *mux.Router) {
  	router.Methods(http.MethodGet).Path("/debug/vars").
  		HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
  			w.Header().Set("Content-Type", "application/json; charset=utf-8")
  			fmt.Fprint(w, "{\n")
  			first := true
  			expvar.Do(func(kv expvar.KeyValue) {
  				if !first {
  					fmt.Fprint(w, ",\n")
  				}
  				first = false
  				fmt.Fprintf(w, "%q: %s", kv.Key, kv.Value)
  			})
  			fmt.Fprint(w, "\n}\n")
  		})
  
  	runtime.SetBlockProfileRate(1)
  	runtime.SetMutexProfileFraction(5)
  	router.Methods(http.MethodGet).PathPrefix("/debug/pprof/cmdline").HandlerFunc(pprof.Cmdline)
  	router.Methods(http.MethodGet).PathPrefix("/debug/pprof/profile").HandlerFunc(pprof.Profile)
  	router.Methods(http.MethodGet).PathPrefix("/debug/pprof/symbol").HandlerFunc(pprof.Symbol)
  	router.Methods(http.MethodGet).PathPrefix("/debug/pprof/trace").HandlerFunc(pprof.Trace)
  	router.Methods(http.MethodGet).PathPrefix("/debug/pprof/").HandlerFunc(pprof.Index)
  }
docs: // Append add debug routes on a router