// *** before: ***
err := fmt.Errorf("save failed: %v and %v", errDisk, errNetwork)
// both errors show up in the text only, errors.Is will not find them
// *** in version 1.20: ***
err := fmt.Errorf("save failed: %w and %w", errDisk, errNetwork)
fmt.Println(errors.Is(err, errDisk)) // true
fmt.Println(errors.Is(err, errNetwork)) // true