事件未定义nodejs

Event is not defined nodejs

我从 patreon 收到一个 webhook,当我启动测试时,我得到这个错误:

(node:636) UnhandledPromiseRejectionWarning: ReferenceError: event is not defined

这是我的代码

const express = require('express');
const bodyParser = require('body-parser');
const app = express();

app.post('/', async (req, res) => {
    let crypto = require('crypto');

    let hash = event.headers['X-Patreon-Signature'],
        hmac = crypto.createHmac("md5", 'patreon-secret-removed ;)'); 

    hmac.update(event.body);

    let crypted = hmac.digest("hex");

    if (crypted === hash) {
        console.log("That's good hash! " + hash);
    } else {
        console.log("Bad hash! " + hash + " crypted " + crypted);
    }
})
app.listen(8080)

我该如何替换或定义事件?

let hash = event.headers['X-Patreon-Signature'] << 什么是事件?

也许这是一个请求,而不是一个事件。