function can't get loaded

Hi,

When I try this code, the function won’t get loaded. At least I don’t get the echo message. How comes?

function custom_login() {
	$creds = array( 'user_login' =>  $_POST['benutzername'], 'user_password' => $_POST['passwort'], 'remember' => true );
	$user = wp_signon( $creds, false );
	if ( is_wp_error($user) ): echo $user->get_error_message(); endif;
	wp_set_current_user($user->ID);
	echo '<h1>HELLO</h1>';
}
add_action( 'after_setup_theme', 'custom_login' );