fix(model): avoid adding timeout on Model.init() buffering to avoid unintentional dangling open handles

lib/connection.js

@@ -818,32 +818,41 @@ Connection.prototype.dropCollection = async function dropCollection(collection)
 /**
  * Waits for connection to be established, so the connection has a `client`
  *
+ * @param {Boolean} [noTimeout=false] if set, don't put a timeout on the operation. Used internally so `mongoose.model()` doesn't leave open handles.
  * @return Promise
  * @api private
  */
 
-Connection.prototype._waitForConnect = async function _waitForConnect() {
+Connection.prototype._waitForConnect = async function _waitForConnect(noTimeout) {
   if ((this.readyState === STATES.connecting || this.readyState === STATES.disconnected) && this._shouldBufferCommands()) {
     const bufferTimeoutMS = this._getBufferTimeoutMS();
     let timeout = null;
     let timedOut = false;
     // The element that this function pushes onto `_queue`, stored to make it easy to remove later
     const queueElement = {};
-    await Promise.race([
-      new Promise(resolve => {
-        queueElement.fn = resolve;
-        this._queue.push(queueElement);
-      }),
-      new Promise(resolve => {
-        timeout = setTimeout(
-          () => {
-            timedOut = true;
-            resolve();
-          },
-          bufferTimeoutMS
-        );
-      })
-    ]);
+
+    // Mongoose executes all elements in `_queue` when initial connection succeeds in `onOpen()`.
+    const waitForConnectPromise = new Promise(resolve => {
+      queueElement.fn = resolve;
+      this._queue.push(queueElement);
+    });
+
+    if (noTimeout) {
+      await waitForConnectPromise;
+    } else {
+      await Promise.race([
+        waitForConnectPromise,
+        new Promise(resolve => {
+          timeout = setTimeout(
+            () => {
+              timedOut = true;
+              resolve();
+            },
+            bufferTimeoutMS
+          );
+        })
+      ]);
+    }
 
     if (timedOut) {
       const index = this._queue.indexOf(queueElement);

lib/model.js

@@ -1112,7 +1112,7 @@ Model.init = function init() {
     );
     if (autoCreate == null) {
       // `autoCreate` may later be set when the connection is opened, so wait for connect before checking
-      await conn._waitForConnect();
+      await conn._waitForConnect(true);
       autoCreate = utils.getOption(
         'autoCreate',
         this.schema.options,