[BREAKING CHANGE] add _. for TXT

Just realized I can't put TXT on CNAME :/

src/client.js

@@ -35,12 +35,12 @@ const acme_prefix = '/.well-known/acme-challenge/';
 const listener = async function (/** @type {import('http').IncomingMessage} */ req, /** @type {import('http').ServerResponse} */ res) {
     try {
         if (req.url.startsWith(acme_prefix)) {
-            if (client.challengeCallbacks) {
+            if (client.challengeCallbacks[req.headers.host]) {
                 res.writeHead(200, {
                     // This is important :)
                     'content-type': 'application/octet-stream'
                 });
-                res.write(client.challengeCallbacks());
+                res.write(client.challengeCallbacks[req.headers.host]());
             } else {
                 res.writeHead(404)
             }

src/sni.js

@@ -22,10 +22,16 @@ function getCertCachePath(host) {
     return path.join(certsDir, hash.substr(0, 2), hash.substr(2), host);
 }
 
+/**
+ * @param {string} host
+ */
 async function findMaintainerEmail(host) {
     return await findTxtRecord(host, record_email_prefix);
 }
 
+/**
+ * @param {string} host
+ */
 async function buildCache(host) {
     const dir = getCertCachePath(host);
     const keyP = path.join(dir, 'privateKey.pem');
@@ -64,6 +70,9 @@ async function buildCache(host) {
 
 }
 
+/**
+ * @param {string} servername
+ */
 async function getKeyCert(servername) {
     let cache = resolveCache[servername];
     await ensureDir(certsDir);

src/util.js

@@ -17,8 +17,12 @@ async function ensureDir(dir) {
     }
 }
 
+/**
+ * @param {string} host
+ * @param {string} prefix
+ */
 async function findTxtRecord(host, prefix, required = true) {
-    const resolve = await axios(`https://dns.google/resolve?name=${encodeURIComponent(host)}&type=TXT`);
+    const resolve = await axios(`https://dns.google/resolve?name=_.${encodeURIComponent(host)}&type=TXT`);
     if (resolve.data.Answer) {
         for (const head of resolve.data.Answer) {
             if (!head.data.startsWith(prefix))