shadowfacts.net/lib/activitypub/webfinger.ts

import express, { Router } from "express";

const domain = process.env.DOMAIN;

export default function webfinger(router: Router) {
	router.get("/.well-known/webfinger", (req, res) => {
		res.json({
			"subject": `acct:blog@${domain}`,
			"links": [
				{
					"rel": "self",
					"type": "application/activity+json",
					"href": `https://${domain}/ap/actor`
				}
			]
		});
		res.end();
	});
}