Nextjs sitemap header error

const setHeader = async (context: GetServerSidePropsContext, chunk: { loc: string }[]) => {
  // cache it for 1 day
  context.res.setHeader('Cache-Control', 's-maxage=86400, stale-while-revalidate');
  context.res.setHeader('Content-Type', 'text/xml');

  const sitemaps = await getServerSideSitemap(context, chunk);

  context.res.write(sitemaps);
  context.res.end();

  return { props: {} };
};

error - Error: Cannot set headers after they are sent to the client

code: 'ERR_HTTP_HEADERS_SENT',
page: '/sitemap/[sitemapId]'