Generators

A generator is a function that returns a channel and starts a goroutine that sends a sequence of values into it. The caller receives the values one at a time with for range, and the goroutine closes the channel after the last value. The caller has no reference to the goroutine. It has only a receive-only channel that produces values until it is closed.

The pattern combines three ideas from earlier chapters. A goroutine owns the channel it writes. A receive-only return type stops the caller from sending or closing. Finally, close signals that no more values will come