Failing to use the 'has_certificate' method

I'm looking to forward http traffic to https, if there is a certificate found. We're using the has_certificate method for this. We've implemented the [example code](https://github.com/auto-ssl/lua-resty-auto-ssl#has_certificate) but nginx fails with the following log line:

lua entry thread aborted: runtime error: rewrite_by_lua(default.conf:34):2: attempt to call method 'has_certificate' (a nil value)

I've placed the code inside the server block listening on port 80.

Any help is greatly appreciated!

Start with the linked has_certificate example and compare it with the OpenResty/nginx server block listening on port 80. Reproduce the reported rewrite_by_lua nil-method error and determine why the method is unavailable there; done means the certificate check works without that runtime error and supports the requested HTTP-to-HTTPS forwarding behavior.

Written by the indexing model from the issue text.