Serverless Offline POST Request Hanging Repro

Repro steps for issue dherault/serverless-offline#1151

Steps to reproduce:

1. Clone repo: git clone [email protected]:s16h/sls-offline-hanging-repro.git
2. Go to repo: cd sls-offline-hanging-repro
3. Install dependencies: npm install
4. Run Serverless Offline: sls offline start
5. Send POST request: curl -X POST http://localhost:3000/dev/test --verbose
6. You'll see that the request hangs.

On the other hand, if you send a GET request (curl -X GET http://localhost:3000/dev/test --verbose), you get a response as expected.