We released version 2.3 of our Force Login Module for Magento 2 which brings some requested features and fixes, here are the highlights of the current release:
The module now supports error pages (e.g. page url does not exist), now showing the error page instead of redirecting to the login page
Previously, observers were used to lookup if a visitor needed to be forced to login. Now, the module uses the core routing chain with a custom routing component. This is a break with backwards compatibility, if you had plugins enabled related to the observers.
Some fixes to increase the support of Magento 2.2
You can fetch the latest version here or go to the official marketplace of Magento 2 and get your update right from Magento Marketplace once approved.