How to work navigate.sendbeacon on ASP.NET

See more:

ASP.NET

Javascript

Using ajax (XmlHttpRequest) on Chrome does not work anymore as indicated on the link below:
https://www.chromestatus.com/feature/4664843055398912

So this site below suggest to use sendBeacon instead:
https://medium.com/@oahehc/synchronous-xmlhttprequest-failing-in-chrome-73-c7537f8156a3

However, the web service does not execute based on the code below. Is there any way to execute the web service. It is much better if the scope of the solution only limits on the used language below.

What I have tried:

I use web service to execute a function:

[WebMethod]
public string CheckOutUser(string id)
{
    return "OK";
}

On the .js file, I have the following code:

$(function () {
    window.onbeforeunload = checkOutUser;
})

function checkOutUser() {
    var url = "TrascriptionService.asmx/CheckOutUser";
    var data = new FormData();
    data.append('id', userId);

    var result = navigator.sendBeacon(url, data);
}