JavaScript中的异步Multiton模式？

Question

我想使用JavaScript中具有异步功能的Multiton模式来缓存性能密集型对象的生成。我提供了一个示例，想知道我是否正确实现了该示例，即是否足以保证同名对象无论异步执行顺序都不会生成两次。

CREATE OR REPLACE FUNCTION vat_total_sum() RETURNS TRIGGER AS $$
BEGIN

   UPDATE goods SET vat_total_sum = NEW.vat_sum / 100 * NEW.vat_percent 
      WHERE goods_id = new.goods_id;

RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER vat_total_sum AFTER INSERT OR UPDATE ON goods
    FOR EACH ROW EXECUTE PROCEDURE vat_total_sum();

const things = new Map();

// in real life, fetch from network or other asynchronous, slow operation
async function slowFunc() {
    return Math.floor(Math.random() * Math.floor(100));
}

class Thing {
    constructor(n) {
        this.n = n;
    }

    static async get(name) {
        let thing = things.get(name);
        if (thing) {
            console.log("Reusing existing", name, "with n=", (await thing).n);
            return thing;
        }
        const promise = slowFunc().then(n => {
            thing = new Thing(n);
            console.log("Creating new", name, "with n=", n);
            return thing;
        }, );
        things.set(name, promise);
        return promise;
    }
}