So, I’m creating a reactjs page where I want to consume a Golang Gorilla Mux api. But whenever I call the api this way:

fetch('http://localhost:8080/commands/', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'credentials': 'same-origin'

            },
            body: JSON.stringify(petitionData),
        })
            .then(res => res.json())
            .then(res => {
                console.log("Response: ", res);
            })
            .catch(error => {

                console.error('Error posting petition:', error);
            });

I get two errors in the console:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8080/commands/. (Reason: CORS preflight response did not succeed). Status code: 405. and Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:8080/commands/. (Reason: CORS request did not succeed). Status code: (null)..
I already went back and fourth with a lot of code in my API. This is how it is now:

func main() {
    r := mux.NewRouter()
    r.Use(enableCORS)
    r.PathPrefix("/getPics/").Handler(http.StripPrefix("/getPics/", http.FileServer(http.Dir("./images"))))
    r.HandleFunc("/", GetUserHandler).Methods("GET")
    r.HandleFunc("/commands/", postCommands).Methods("POST")

    log.Println("Server listening on port 8080...")
    http.ListenAndServe(":8080", r)
}
func enableCORS(next http.Handler) http.Handler {

    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Access-Control-Allow-Origin", "*")
    w.Header().Set("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
    w.Header().Set("Access-Control-Allow-Headers", "Origin, Content-Type, Accept")    
    next.ServeHTTP(w, r)
    
    })
    
    }

Got any ideas about what am I doing wrong?
I tried also calling a function where I passed the pointer enableCors(&w) to a function and adding all the modifications in this way:

func enableCors(w *http.ResponseWriter) {
        header := (*w).Header()
        header.Add("Access-Control-Allow-Origin", "*")
        header.Add("Access-Control-Allow-Methods", "DELETE, POST, GET, OPTIONS")
        header.Add("Access-Control-Allow-Headers", "Content-Type, Authorization, X-Requested-With")
    }

pls help