Bun integration on subscription (Query and Mutation Works, but not Subscription)
I was using bun to run apollo server and nestjs, it worked fine, both Query and Mutation works normally, but when I start working on subscription it always fails to connect (I was using the apollo playground). 

No error was shown, after debugging for a few hours I realized that it's bun runtime that causes the problem. 

I followed this tutorial https://www.apollographql.com/docs/apollo-server/data/subscriptions#basic-runnable-example

Subscription works fine when using nodejs or `ts-node-esm`, but fails as long as I switch to bun.

## Reproduction

- https://github.com/apollographql/docs-examples/blob/main/apollo-server/v4/subscriptions-graphql-ws/src/index.ts

```bash
bun install
bun src/index.ts
```

Bun is a really good tool. It allows me to import typescript from other packages without compiling to JS. I can't really switch to nodejs for the project.

I used WebSocket with bun, it works.
There is no error message, so I don't know what's going on. Apollo Server is probably using some API bun doesn't implement.