Improve application logging

[jfk9w]

Problem

Currently we basically don't use any logging frameworks (except for https://github.com/natefinch/lumberjack for file rolling) and instead implement logging ourselves. The implementation is pretty dumb and it would be nice to use some library for it (more functionality and less supporting costs).

Solution

Choose and implement logging via one of these https://github.com/avelino/awesome-go#logging. It would also probably be benefitial to use structured logging with expanding arbitrary context info on deeper execution levels. I know for certain that logrus can do this, but it seems that it's not in active development anymore (though is supported), so it may be better to opt for zerolog, zap, etc.