test.go

func (f *Future) WaitForCompletionRef(ctx context.Context, client autorest.Client) error {
	ctx, cancel := context.WithTimeout(ctx, client.PollingDuration)
	defer cancel()
	done, err := f.Done(client)
	for attempts := 0; !done; done, err = f.Done(client) {
		if attempts >= client.RetryAttempts {
			return autorest.NewErrorWithError(err, "Future", "WaitForCompletion", f.pt.latestResponse(), "the number of retries has been exceeded")
		}
		// we want delayAttempt to be zero in the non-error case so
		// that DelayForBackoff doesn't perform exponential back-off
		var delayAttempt int
		var delay time.Duration
		if err == nil {
			// check for Retry-After delay, if not present use the client's polling delay
			var ok bool
			delay, ok = f.GetPollingDelay()
			if !ok {
				delay = client.PollingDelay
			}
		} else {
			// there was an error polling for status so perform exponential
			// back-off based on the number of attempts using the client's retry
			// duration.  update attempts after delayAttempt to avoid off-by-one.
			delayAttempt = attempts
			delay = client.RetryDuration
			attempts++
		}
		// wait until the delay elapses or the context is cancelled
		delayElapsed := autorest.DelayForBackoff(delay, delayAttempt, ctx.Done())
		if !delayElapsed {
			return autorest.NewErrorWithError(ctx.Err(), "Future", "WaitForCompletion", f.pt.latestResponse(), "context has been cancelled")
		}
	}
	return err
}