Using Next.js to fetch an audio file and respond it to the client

route.ts

import { NextResponse } from "next/server";

async function GET(
  _request: Request,
  { params }: { params: { url: string } }
) {
  // An audio url, for example, https://xxx/xxx.mp3
  const audioUrl = decodeURIComponent(params.url);
  const headers = new Headers();
  const res = await fetch(audioUrl).then((res) => {
    headers.set("Content-Type", res.headers.get("Content-Type")!);
    headers.set("Content-Length", res.headers.get("Content-Length")!);

    return res.body;
  });

  return new NextResponse(res, { status: 200, headers });
}