Do I need to run a service with an API and a website on different ports?

Question

go

Tell me what the problem is, when I launch the api and the site (I mean the visual component), then it is impossible to access the api and returns 404 page not found, if I run it on different ports it works fine.

r := mux.NewRouter()
        //если убрать эти строки то api работает нормально
       //если не убрать то невозможно будет получить доступ к /api/notes
  fs := http.FileServer(http.Dir("public"))
  r.PathPrefix("/").Handler(fs)
        //
  r.HandleFunc("/api/notes", GetNoteHandler).Methods("GET")
  r.HandleFunc("/api/notes", PostNoteHandler).Methods("POST")
  r.HandleFunc("/api/notes/{id}", PutNoteHandler).Methods("PUT")
  r.HandleFunc("/api/notes/{id}", DeleteNoteHandler).Methods("DELETE")
  server := &http.Server{
    Addr:
    ":8080",
    Handler: r,
  }
  log.Println("Listening...")
  err := server.ListenAndServe()
  fmt.Println(err)

Answer 1

All requests are processed through FileServerbecause the root level is specified. Do e.g. for files /public, then the api will work. You will also need to remove this prefix withhttp.StripPrefix

fs := http.StripPrefix("/public",  http.FileServer(http.Dir("public")))
r.PathPrefix("/public").Handler(fs)

Answer 2

Different applications (processes) cannot run on the same port.
With such a code, an error will be displayed in the application log and the process will immediately end with an error code.
log.Fatal(server.ListenAndServe())
We also need to remember about CORS.