Concurrency

Introduction Testing concurrent code in Go can be challenging, especially when dealing with timing issues. One common problem is ensuring goroutines, Go’s lightweight threads, have finished their tasks. Traditional techniques often incorporate time.Sleep, but this can slow down tests or make them unreliable. Fortunately, Go 1.25 introduced the testing/synctest package into the standard library (after first being available experimentally in Go 1.24). It helps tackle these issues by providing a deterministic way to test concurrent code without the usual timing trade-offs. ...

In Go, using a mutex with defer might seem like an elegant and safe way to manage your code by ensuring resources are properly released. However, a common mistake lurks when this pattern is used inside loops. When working with mutexes, never do this: func broadcast(ctx context.Context, msgCh <-chan Message) { for { select { case msg := <-msgCh: s.mu.Lock() defer s.mu.Unlock() // ❌ Avoid this // Use the shared resource here case <-ctx.Done(): return } } } This seemingly harmless pattern can cause unexpected behavior and should be avoided. Let’s look into why this happens and how to handle it correctly. ...