Unexpected add action function in WP plugin

I’m trying to build out a plugin from a tutorial that will access my google calendar. So far I’m stuck on just trying to register the widget. Here is a link to the tutorial:

https://code.tutsplus.com/tutorials/how-to-create-a-google-calendar-plugin-for-wordpress–cms-32710

I keep running into the problem of the ‘add_action’ function at the bottom of the script. I keep getting an error of ‘syntax error, unexpected ‘add_action’. I’m not even sure I’m building this correctly.

<?php

/** 
 * Plugin Name: My gCal Plugin
 * Description: Displays upcoming events from Google calender
 * version: 1.0.0
 * 
 * 
 */


class My_gCal_Widget extends WP_Widget
{
    public function __construct()
    {
        parent::__construct(
            'my_gcal_widget',
            'My_gCal_Widget',
            array(
                'classname' => 'my-gcal-widget',
                'description' => 'Shows events from a calendar'
            )
        );
    }

    public function widget($args, $instance)
    {
    }
}

add_action('widgets_init', function () {
    register_widget('My_gCal_Widget');
});