What hook to use to redirect based on $post

Question

Trying to add an action to redirect based on if user is not logged in and is accessing certain post types. Problem is, during template_redirect, $post is NULL and other ones the headers seem to have already been sent so it won't redirect. What would be the appropriate action to use here?

add_action( 'template_redirect', 'mytheme_restrict_user_content' );
function mytheme_restrict_user_content(){
    if (!is_user_logged_in() ) {
        $restrict = false;
        $restricted_post_types = array('documentlibrary', 'events');
        if ( in_array( $post->post_type, $restricted_post_types ) ){
            $restrict = true;
        }
        if ($restrict){
            auth_redirect();
        }
    }
}

Answer 1

add_action( 'pre_get_posts', 'mytheme_restrict_user_content' );

function mytheme_restrict_user_content( $query ){
  $restricted_post_types = array('documentlibrary', 'events');
  if ( is_main_query() && is_singular($restricted_post_types) && ! is_user_logged_in() ) {
    $redirect = set_url_scheme('http://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI']);
    wp_redirect( wp_login_url($redirect, true) );
    exit();
  }
}

I don't use auth_redirect because that function check if the user is logged in, but we already know that user is not logged in.