Magento 2: My custom plugin return 404 page in admin panel
<p>I am trying to make my first plugin in Magento 2.0.2.
But magento admin panel show me 404 page.
I've read a few tutorials, but it does not help.</p>

<p>app/code/MyCustom/ProductsGroups/etc/module.xml</p>

<pre><code>&lt;?xml version="1.0"?&gt;
&lt;config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd"&gt;
    &lt;module name="Products_Groups" setup_version="1.0.0"&gt;
    &lt;/module&gt;
&lt;/config&gt;
</code></pre>

<p>app/code/MyCustom/ProductsGroups/etc/adminhtml/menu.xml</p>

<pre><code>&lt;?xml version="1.0"?&gt;
&lt;config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Backend:etc/menu.xsd"&gt;
    &lt;menu&gt;
        &lt;add id="Products_Groups::groups" title="Products groups" module="Products_Groups" parent="Magento_Catalog::inventory" action="groups/list/" resource="Products_Groups::groups"/&gt;
    &lt;/menu&gt;
&lt;/config&gt;
</code></pre>

<p>app/code/MyCustom/ProductsGroups/etc/adminhtml/routes.xml</p>

<pre><code>&lt;?xml version="1.0"?&gt;
&lt;config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:App/etc/routes.xsd"&gt;
    &lt;router id="admin"&gt;
        &lt;route id="groups" frontName="groups"&gt;
            &lt;module name="Products_Groups"/&gt;
        &lt;/route&gt;
    &lt;/router&gt;
&lt;/config&gt;
</code></pre>

<p>app/code/MyCustom/ProductsGroups/Controller/Adminhtml/List/Index.php</p>

<pre><code>&lt;?php

namespace Axiom\Groups\Controller\Adminhtml\Groups;

class Index extends \Magento\Backend\App\Action
{
    public function execute()
    {
        die ("test test test");
    }
}
</code></pre>

<p>Can some one help me?</p>