Build multi-turn conversations error unknown field "usageMetadata"

Hi! I just tried to implement Gemini API for my Golang Gin project, I just following the instruction on this page:

But, when I try to run my apps, it return the unknown field “usageMetadata” error when it try to do the “cs.SendMessage()”.

Btw this is how I implement my code:

func (srv *GeminiService) Chat(prompt *request.GeminiText) (error, []string) {
	ctx := context.TODO()

	client, err := genai.NewClient(ctx, option.WithAPIKey(config.EnvGeminiApiKey()))

	if err != nil {
		return err, nil
	}

	defer func(client *genai.Client) {
		err := client.Close()
		if err != nil {
			log.Fatalln(err)
		}
	}(client)

	model := client.GenerativeModel("gemini-pro")
	cs := model.StartChat()

	resp, err := cs.SendMessage(ctx, genai.Text(prompt.Text))

	if err != nil {
		return err, nil
	}

	var results []string

	for _, candidate := range resp.Candidates {
		if candidate.Content != nil {
			for _, part := range candidate.Content.Parts {
				if text, ok := part.(genai.Text); ok {
					results = append(results, string(text))
				}
			}
		}
	}

	return nil, results
}

Am I do anything wrong?

*screenshot when I comment the error handling and let the program to print the error: