如何使用单个客户端ID和API密钥用于多个域

I have main domain ("i.e. http://www.example.com") and sub-domain ("i.e.http://*.example.com"). I want to use Google Drive File Picker API, for that I want to use single client ID and API keys for all my sub domain. Conclusion of my research is that, we need to create a separate Client ID and API keys for each sub Domain but, I want to use single Client ID and API Key for all sub-domain. How can I achieve this.

Thank you.