Bug Description

When using fetch to make non-GET/HEAD http2 requests, the function call hangs indefinitely. Passing in an empty string in place of the body fixes this issue.

Reproducible By

The following js script triggers the issue on undici v6.2.1

'use strict'

const { fetch, Client } = require('undici')

async function main () {
    const client = new Client("https://google.com", { allowH2: true });
    const res = await fetch("https://google.com", {
        dispatcher: client,
        baseURL: 'https://google.com',
        url: 'https://google.com/',
        method: "POST",
    })

    const data = await res.text()
    console.log('response received', res.status)
    console.log('headers', res.headers)
    console.log('data', data)
}
main()

Expected Behavior

The function call should send the request with an empty body.

Environment

macOS 14.0, node v20.8.1, undici v6.2.1

Additional context

I believe the issue is closely related to #2258 , but while this PR had only fixed GET/HEAD requests, this actually affects all kinds of requests.