In this chapter we covered a lot of ground. We learned different techniques for gracefully shutting down programs using signaling channels, which is especially important when our code has some work to do before it can exit. We saw that deferring the reporting of fatal errors at the start of our program can give our other deferred functions a chance to execute before the process ends.

We also discovered how easy it is to interact with MongoDB using the mgo package, and how to use BSON types when describing concepts for the database. The bson.M alternative to map[string]interface{} helps us keep our code more concise, while still providing all the flexibility we need when working with unstructured or schemaless data.

We learned about message queues and how they allow us to break apart the components of a system into isolated and specialized micro-services. We started an instance of NSQ by first running the lookup daemon nsqlookupd, before running a single nsqd instance and connecting...