Wait for goroutines to exit

Given a goroutine spawned by the system, there must be a way to wait for the goroutine to exit. There are two popular ways to do this:

• Use a sync.WaitGroup. Do this if there are multiple goroutines that you want to wait for

    var wg sync.WaitGroup
    for i := 0; i < N; i++ {
      wg.Add(1)
      go func() {
        defer wg.Done()
        // ...
      }()
    }
  
    // To wait for all to finish:
    wg.Wait()
  

• Add another chan struct{} that the goroutine closes when it's done. Do this if there's only one goroutine.

    done := make(chan struct{})
    go func() {
      defer close(done)
      // ...
    }()
  
    // To wait for the goroutine to finish:
    <-done