为什么 go fiber 无法解析 alipay 的 notify 回调的参数？

我现在使用的是 go fiber ，我知道的是这家伙用的是 fasthttp 。

是这样的，我现在要解析支付宝返回来的回调。我发现 fiber 解析出来都是空的，但其它有两三个字段是有的：

{
        "notify_time": null,
        "notify_type": null,
        "notify_id": null,
        "app_id": null,
        "charset": [
                "utf-8"
        ],
        "version": [
                "1.0"
        ],
        "sign_type": null,
        "sign": [
                "CPwn0wkSwa7qjV+k8/RHywHyPpL7kdmadp6QSZuw+NJe5vQ8vgKJHtLKMOA8RxPTY+BWhwEqN86F3RrDU0x6gj2UttN6qOauL4ZOer7KanWmmDEjnIR5YLqPibAbo8FyuCwtNQsUXsC8A8DxjfmJg5bTyEXxcF4UMFCvDfcC55eY+UVkcu0dt6KjLag+mUOMj/+PA5KBARkegfDi0yW4J78pv5Fgb9lD1u5bM9xEHDxOt1Xo6Jf63cnsWm5ccZ+cBQFQFKr4mSUAp0gIP1o1kzvUVJqr9ISK2HFGK8ED26OjuH8bWrtcepd08I8MxvZ170oRP1in9Hpk8wEwDZjyqw=="
        ],
        "trade_no": null,
        "out_trade_no": null,
        "out_biz_no": null,
        "buyer_id": null,
        "buyer_logon_id": null,
        "trade_status": null
}

fiber 的代码如下：

var input common.AlipayNotifyResponse

	if err := c.BodyParser(&input); err != nil {
		fmt.Println("failed to parse JSON input")
		return errors.New("failed to parse JSON input")
	}

然后我就怀疑是 fiber 的问题，试了一下用原生的 net/http 写：

func handlePost(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Headers", "*")
	r.ParseForm()

	fmt.Println(utils.PrettyJson(r.Form))
}

发现是可以解析的：

{
        "app_id": [
                "902100sdff"
        ],
        "auth_app_id": [
                "902100sdff"
        ],
        "buyer_id": [
                "902100sdff"
        ],
        "buyer_pay_amount": [
                "8.00"
        ],
        "charset": [
                "utf-8"
        ],
        "fund_bill_list": [
                "[{\"amount\":\"8.00\",\"fundChannel\":\"ALIPAYACCOUNT\"}]"
        ],
        "gmt_create": [
                "2023-08-06 17:48:28"
        ],
        "gmt_payment": [
                "2023-08-06 17:48:33"
        ],
        "invoice_amount": [
                "8.00"
        ],
        "notify_id": [
                "202308060122217483409dd7380500601571"
        ],
        "notify_time": [
                "2023-08-06 17:48:34"
        ],
       }

现在已经有好几个接口用 fiber 写好了，不太想大改。就想问问为什么 fiber 会解析不了？有没有哪里是我要注意的