move res.send

src/server/routes/apiv3/slack-bot.js

@@ -7,7 +7,11 @@ module.exports = (crowi) => {
   this.app = crowi.express;
   const { boltService } = crowi;
 
-  router.post('/', boltService.receiver.requestHandler.bind(boltService.receiver));
+  router.post('/', boltService.receiver.requestHandler.bind(boltService.receiver), (req, res) => {
+
+    // for verification request URL on Event Subscriptions
+    res.send(req.body);
+  });
 
   return router;
 };

src/server/service/bolt.js

@@ -30,9 +30,6 @@ class BoltReciever {
     };
 
     await this.bolt.processEvent(event);
-
-    // for verification request URL on Event Subscriptions
-    res.send(req.body);
   }
 
 }