Deno.serve() doesn't stream, part 2

client.js

const wait = async (ms) => new Promise((r) => setTimeout(r, ms));

fetch('https://localhost:8000', {
  duplex: 'half',
  method: 'post',
  body: new ReadableStream({
    async start(controller) {
      await wait(1000);
      controller.enqueue('This ');
      await wait(1000);
      controller.enqueue('is ');
      await wait(1000);
      controller.enqueue('a ');
      await wait(1000);
      controller.enqueue('slow ');
      await wait(1000);
      controller.enqueue('request.');
      controller.close();
    },
  }).pipeThrough(new TextEncoderStream())
}).then((r) => r.body.pipeThrough(new TextDecoderStream())).then((r) => r.pipeTo(new WritableStream({
  write(value) {
    console.log(value);
  }, 
  close() {
    console.log('Stream closed.');
  }
}))).then(() => console.log('Done writing stream')).catch(console.warn);

streamtest.js

// ./deno run -A --unsafely-ignore-certificate-errors=localhost --unstable streamtest.js
let cert = Deno.readTextFileSync('certificate.pem');
let key = Deno.readTextFileSync('certificate.key');

let responseInit = {
  duplex: 'half',
  headers: {
    'Content-Type': 'text/plain; charset=UTF-8',
    'Cross-Origin-Opener-Policy': 'unsafe-none',
    'Cross-Origin-Embedder-Policy': 'unsafe-none',
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Private-Network': 'true',
    'Access-Control-Allow-Headers': 'Access-Control-Request-Private-Network',
    'Access-Control-Allow-Methods': 'OPTIONS,POST,GET,HEAD,QUERY',
  }
};

let server = Deno.serve({
  cert,
  key
}, async (request) => {
  try {
    if (request.method === 'OPTIONS') {
      return new Response(null, responseInit);
    }
    if (request.method === 'POST') {
      return new Response(
        request.body.pipeThrough(new TextDecoderStream())
        .pipeThrough(
          new TransformStream({
            transform(value, c) {
              console.log(value);
              c.enqueue(value.toUpperCase());
            },
            flush() {
              console.log('flush');
            },
          })
        )
        .pipeThrough(new TextEncoderStream()), responseInit
      );
    }
  } catch (e) {
    console.log(e);
  }
});

./deno run -A --unstable --unsafely-ignore-certificate-errors=localhost client.js