When you loaded your template file, you already passed the 'template_redirect' hook, which is too late (See: Plugin/Action API Reference). You need to set the add_action call in your functions.php file, which is loaded before the after_setup_theme hook - which is the first available hook for themes.

When you loaded your template file, you already passed the 'template_redirect' hook, which is too late (See: Plugin/Action API Reference). 

You need to set the add_action call in your functions.php file, which is loaded before the after_setup_theme hook - which is the first available hook for themes.