Add Fetch Does Not Work In API Serverless Function as a Next.js TIL

nextjs/fetch-does-not-work-in-api-serverless-function.md

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+# Fetch Does Not Work In API Serverless Function
+
+Next.js ships with [its own implementation of
+`fetch`](https://nextjs.org/docs/app/api-reference/functions/fetch) that
+extends the [native `fetch`
+API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API).
+
+I ran into a bug recently that was only reproducible in production. I had a
+Next.js API function that was `POST`ing to another API endpoint using `fetch`.
+I tested it several ways in development. It worked great. However, once the
+feature was in production, it was silently failing. After some `console.log`
+debugging, I discovered that the target API was getting an empty `body` in the
+`POST` request.
+
+I don't know the specifics of why, but somehow the `fetch` implementation
+running in the Vercel serverless function environment apparently strips out the
+`body` of a POST request.
+
+The solution, for me, was to add the
+[`node-fetch`](https://github.com/node-fetch/node-fetch) package and import
+that version of fetch in my API function. Once I made that change, my feature
+was working again.
+
+[source](https://github.com/vercel/vercel/discussions/4971)