Glassfy.initialize(this, "8NOV6FQBHHRJ4F9N2HV0HUXOQ5LL0QA3", false, null);
Glassfy.offerings((offers, error) -> {
    Sku sku = null;
    if (offers != null) {
        for (Offering o : offers.getAll()) {
            if (o.getOfferingId().equals("my_offering") && o.getSkus().size() > 0) {
                sku = o.getSkus().get(0);
                break;
            }
        }
    }
    if (sku == null) { return; }
    Glassfy.purchase(this, sku, (transaction, err) -> {
        if (transaction != null) {
            for (Permission p : transaction.getPermissions().getAll()) {
                if (p.getPermissionId().equals("premium") && p.isValid()) {
                    // unlock premium
                }
            }
        }
    });
});