From 3c5d5b55c39ff120245b3404bc7891820dd285dd Mon Sep 17 00:00:00 2001
From: JJ Kasper <jj@jjsweb.site>
Date: Wed, 3 Nov 2021 13:28:47 -0500
Subject: [PATCH] Add note about HMR WebSocket with express to upgrading
 (#30905)

x-ref: https://github.com/vercel/next.js/issues/30491#issuecomment-957865735

## Documentation / Examples

- [x] Make sure the linting passes by running `yarn lint`
---
 docs/upgrading.md | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/docs/upgrading.md b/docs/upgrading.md
index 55c7c39d3128e..15281fdcbb269 100644
--- a/docs/upgrading.md
+++ b/docs/upgrading.md
@@ -71,6 +71,14 @@ location /_next/webpack-hmr {
 }
 ```
 
+For custom servers, such as `express`, you may need to use `app.all` to ensure the request is passed correctly, for example:
+
+```js
+app.all('/_next/webpack-hmr', (req, res) => {
+  nextjsRequestHandler(req, res)
+})
+```
+
 ### Webpack 4 support has been removed
 
 If you are already using webpack 5 you can skip this section.