Concurrency Section Improvements

[GeorgeMac]

What I think we need to add in order to feel that concurrency is complete for now.

• [x] supervising goroutines (e.g. tracking them with wait groups or communicating with them via channels)
• [x] examples of leaky concurrency + architectural solutions to avoid it.
• [ ] bounded concurrency (using a "pool" of goroutines, rather than fire off any number of them)
• [ ] testing concurrency + the race detector

Please contribute to this Issue thread so that we can track here the topics we want to talk about.

[brettbuddin]

Indeed. A hard and fast rule is:

If you use the go keyword, you need to be asking yourself "How will this goroutine terminate? Will it ever? How do I ensure that it has a potential exit case."