Classic Concurrency Exercises in Go

Two goroutines are running. How do you make them take strict turns, so that the first prints 1, the second prints 2, the first prints 3, and so on up to 10?

The two goroutines share no turn counter, and the scheduler promises nothing about which one runs next. Any order between them has to come from a synchronizing operation that the program performs on purpose. Four small exercises have become the standard way to practice this. They cover taking turns, passing an object back and forth, sharing a bounded buffer, and sharing resources without a deadlock.