How to enable more PHP Extensions?

[StanleyBonhomme]

I currently have a project with the Offline Mall plugin for OctoberCMS. When I try to access the checkout page I get an error. When I check the logs I the following error:

RuntimeException: Missing BC Math or GMP extension. in /var/www/html/plugins/offline/mall/vendor/hashids/hashids/src/Math.php:113

After some research it seems as the BC Math or GMP extension is not enabled. How can I go about enable these extensions in my docker image?

[TimFoerster]

You can write your own container which installs bc math.
RUN docker-php-ext-install bcmath

You can also use mine docker container foersterwerbung/ocb which already have bcmath included.