Golang REST API PUT and DELETE request doest work when calling from HTML page using Javascript

I am trying to write a REST API in Go, all the methods are working fine when I run through postman, but when calling the PUT and Delete methods from the HTML page using JAVA Script function it's not working. Are there any alternatives for the same?

Here are my Go Handlers in main.go file.

func main() {
	router := mux.NewRouter()
	router.HandleFunc("/", HomePageHandler).Methods("GET")
	router.HandleFunc("/demo", CreateDemoDetail).Methods("POST") // Add New row
	router.HandleFunc("/demo", GetAllDemoDetails).Methods("GET") // Fetch all details
	router.HandleFunc("/demo/{id}", GetDemoDetail).Methods("GET") // Fetch Single row
	router.HandleFunc("/demo", UpdateDemoDetails).Methods("PUT") // Update Single row
	router.HandleFunc("/demo", DeleteDemo).Methods("DELETE")     // Delete Single row
	log.Fatal(http.ListenAndServe(":8080", router))
}

Following is the Java Script function which calls the Handlers,

 function submitForm(reqtype){
          var form = document.getElementById("demoform");      
    
          if (reqtype == "Delete"){
            form.action = 'http://localhost:8080/demo';
           form.method='PUT';      
          }
          if (reqtype == "Update"){
            form.action = 'http://localhost:8080/demo';
            form.method='DELETE';      
    
          }      
    
          form.submit();
        }
      </script>

If i change the handler to
router.HandleFunc("/updatedemo", UpdateDemoDetails).Methods("POST") than just /demo and the method to POST it works from java script, but not when its demo/ and the method is PUT/Delete.

Interestingly it works perfectly with Postman when the endpoints are demo/ or get demo and method are POST/GET/PUT/Delete. But not from HTML form with Javascript call.

What is the best approach I should take?

The method attribute only supports the GET and POST HTTP verbs.

To use PUT or DELETE you would need to make the request with fetch or XMLHttpRequest.

I would look at CORS (https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) if your web server is running other host / port than your API.

As suggested in comments, check your browsers JS logs / console. There should be clear error messages if CORS is your problem.