}
	_, err = fmt.Fprintf(f, "mode: %s\n", cfg.BuildCoverMode)
	if err != nil {
		base.Fatalf("%v", err)
	}
	coverMerge.f = f
}

// mergeCoverProfile merges file into the profile stored in testCoverProfile.
// It prints any errors it encounters to ew.
func mergeCoverProfile(ew io.Writer, file string) {
	if coverMerge.f == nil {
		return
	}
	coverMerge.Lock()
	defer coverMerge.Unlock()