使用即将推出的页面阻止对我的网站的公共访问

I have a Rails website and it is live under root url. I want to block public access to it. Preferably with a Coming Soon page. But I still want to access it "maybe with a login, or any other way" so that I can deploy my codes, continue adding content until I'm ready for public release.I have a Rails website and it is live under roo