Update settings UI from a background closure

In my settings UI I make a http request to a service and based on the results I want to update the settings UI.

I'm developing on a Mac using Swift.

httpRequest("http://example.com") { result in 
   // change some settings UI values

   callback(.refresh, nil)
}

This does not work, so I tried to put the refresh on the main thread like so:

httpRequest("http://example.com") { result in 
    // change some settings UI values
    
    DispatchQueue.main.async {
        callback(.refresh, nil)
    }
}

But this does not work either.

Any ideas on how to get this to work?