fix: 再試行抑制

app.js

@@ -1,10 +1,30 @@
-const { App } = require("@slack/bolt");
+const { promisify } = require("util");
+const { App, ExpressReceiver } = require("@slack/bolt");
 const daraz = require("./");
 
+class Receiver extends ExpressReceiver {
+  /**
+   * @param {import("express").Request} req
+   * @param {import("express").Response} res
+   */
+  requestHandler(req, res) {
+    // NOTE: See also https://api.slack.com/events-api#errors
+    res.header("x-slack-no-retry", "1");
+    if (req.headers["x-slack-retry-reason"] === "http_timeout")
+      return promisify(res.end)();
+
+    return super.requestHandler(req, res);
+  }
+}
+
+const receiver = new Receiver({
+  signingSecret: process.env.SLACK_SIGNING_SECRET,
+});
+
 const app = daraz(
   new App({
     token: process.env.SLACK_BOT_TOKEN,
-    signingSecret: process.env.SLACK_SIGNING_SECRET,
+    receiver,
   })
 );