Consider switching form logrus to another logging package

As mentioned in https://github.com/sirupsen/logrus/commit/4ecd9a62bd57b6533e0d87ae23a6b10adc32b5ce, logrus is in maintenance mode. One of the big shortcomings with logrus is that it's hard to test with it; logrus fires a Goroutine to write a message, but there's no way to flush or wait for the output to be ready: https://github.com/sirupsen/logrus/issues/435

https://github.com/uber-go/zap looks like it's pretty active and a solid alternative.