How to type decorateReply of fastify

noCacheReplyPlugin.ts

import { FastifyInstance, FastifyReply } from 'fastify';
import fp from 'fastify-plugin';

// To use it thisway: reply.noCache().code(200).send({});
declare module 'fastify' {
  interface FastifyReply {
    noCache(): FastifyReply;
  }
}

const headersToPreventHTTPCaching = {
  'Cache-Control': 'no-cache, no-store, max-age=0, must-revalidate',
  Pragma: 'no-cache',
  Expires: 'Fri, 01 Jan 1990 00:00:00 GMT',
};

const noCacheReply = fp(async (fastify: FastifyInstance) => {
  function noCache(this: FastifyReply): FastifyReply {
    const reply = this;
    reply.headers(headersToPreventHTTPCaching);

    return reply;
  }

  fastify.decorateReply<() => FastifyReply>('noCache', noCache);
});

export default noCacheReply;