how to modify the request body in a middleware

[tobylai-toby]

I am writing a bot for a platform called kook, so i am writing a webhook.
the request from the platform is compressed using zlib so i need to write a middleware to decompress the data, modify the request body and pass it to the app.
the middleware is like:

createMiddleware(async (c, next) => {
    if (c.req.method != "POST") {
      await next();
      return;
    }
    const req = c.req.raw.clone();
   // some code
    let res="the decompressed text result, it's json text";
    let resReadableStream = new ReadableStream({
      start(controller) {
        controller.enqueue(new TextEncoder().encode(res));
        controller.close();
      },
    });
    c.req.raw = new Request(req, {
      body: resReadableStream,
      headers: { "Content-Type": "application/json" },
    });
    await next();
  });

but when i try to call await c.req.json() in app.post("/foo",func), it throws ��N�0"... is not valid JSON 'x', "x�. (i checked the res varible and found it was correct.)

After searching in the documentation, i didn't find the right way to modify the request body before next()(i only found the way to modify response after that). so i hope to find some clues here.

[tobylai-toby]

Environment:
deno 1.43.6

[tobylai-toby]

hono: 4.5.4

[tobylai-toby]

it seems impossible so now i use Context.set() / get() instead

[rogeriopavan]

I dont now about alter all req, mas to add a value to a req i use:

context.req["myVariable"] = "myvariable"