// create a new webtransport.Server, listening on (UDP) port 443
s := webtransport.Server{
    H3: http3.Server{Addr: ":443"},
}

// Create a new HTTP endpoint /webtransport.
http.HandleFunc("/webtransport", func(w http.ResponseWriter, r *http.Request) {
    conn, err := s.Upgrade(w, r)
    if err != nil {
        log.Printf("upgrading failed: %s", err)
        w.WriteHeader(500)
        return
    }
    // Handle the connection. Here goes the application logic. 
})

s.ListenAndServeTLS(certFile, keyFile)

var d webtransport.Dialer
rsp, conn, err := d.Dial(ctx, "https://example.com/webtransport", nil)
// err is only nil if rsp.StatusCode is a 2xx
// Handle the connection. Here goes the application logic.