Tried to install / setup on a Crystal 1.0.0 box,
After cloning git and ' shards install' it spills out an error.

This is inelegant behavior, using resources that don't need to be used, because only http origin requests should be proxied in the first place. Please do your voodoo regex magic to ensure https resources aren't proxied unnecessarily.

The hmac security in this camo implementation is fine. Except you print out the expected key in case it doesn't match. That means it's trivial to generate urls.

Do not output the expected checksum in request.cr:23 it makes the entire hmac-security useless.