ValueType只能等待一次,这意味着什么?

我想使用 ValueTask 。我在某个地方发现“ValueTask只能等待一次”。我等不及这个方法了 GetMoney 多次还是什么?如果是,我应该如何更改代码?

public class CreditCardService
{
    private Dictionary<int, int> _cache = new Dictionary<int, int>()
    {
        { 1, 500 },
        { 2, 600 }
    };

    public async ValueTask<int> GetMoney(int userId)
    {
        if (_cache.ContainsKey(userId))
        {
            return _cache[userId];
        }

        //some asynchronous operation:
        Random rnd = new Random();
        var money = rnd.Next(100);

        _cache[userId] = money;
        return await Task.FromResult(money);
    }
}

var creditCardService = new CreditCardService();
Console.WriteLine(await creditCardService.GetMoney(1));
Console.WriteLine(await creditCardService.GetMoney(3));
Console.WriteLine(await creditCardService.GetMoney(3));