How can you stop a goroutine if the expected value has not been reached yet?

In Go, to stop a goroutine that is waiting for a value but that value may not arrive, channels with timeout or a cancellable context are usually used.

Example with timeout using select and time.After:

select {
case val := <-ch:
    // received value, continue work
case <-time.After(time.Second * 5):
    // timeout, stop the goroutine
}

Another way is to use a context (context.Context), which can be canceled from outside:

ctx, cancel := context.WithCancel(context.Background())

go func() {
    select {
    case val := <-ch:
        // process val
    case <-ctx.Done():
        // stop the goroutine
    }
}()

// somewhere in the code, call cancel() to stop the goroutine

Thus, the goroutine will not wait indefinitely and can terminate correctly.