--log-output=file does not always flush all logs to the file after k6 is done

[na--]

We don't have the same "done" channel for file log outputs that we do for loki:

k6/cmd/root.go

Lines 292 to 309 in 1e28a3e

	case strings.HasPrefix(line, "loki"):
	ch = make(chan struct{})
	hook, err := log.LokiFromConfigLine(c.ctx, c.fallbackLogger, line, ch)
	if err != nil {
	return nil, err
	}
	c.logger.AddHook(hook)
	c.logger.SetOutput(ioutil.Discard) // don't output to anywhere else
	c.logFmt = "raw"
	case strings.HasPrefix(line, "file"):
	hook, err := log.FileHookFromConfigLine(c.ctx, c.fallbackLogger, line)
	if err != nil {
	return nil, err
	}
	c.logger.AddHook(hook)
	c.logger.SetOutput(ioutil.Discard)

So this code is not guaranteed to run:

k6/log/file.go

Lines 129 to 136 in 1e28a3e

	case <-ctx.Done():
	if err := h.bw.Flush(); err != nil {
	h.fallbackLogger.Errorf("failed to flush buffer: %w", err)
	}
	if err := h.w.Close(); err != nil {
	h.fallbackLogger.Errorf("failed to close logfile: %w", err)
	}

I found this while writing some integration tests so I have a bugfix that I will submit shortly.