tslint Error - Shadowed name: 'err' : <p>tslint is currently throwing the following error</p>

<pre><code>Shadowed name: 'err'
</code></pre>

<p>Here is the code</p>

<pre><code>fs.readdir(fileUrl, (err, files) =&gt; {
        fs.readFile(path.join(fileUrl, files[0]), function (err, data) {
            if (!err) {
                res.send(data);
            }
        });
    });
</code></pre>

<p>Anybody have a clue on what the best way would be to solve this and what the error even means?</p>
