Open a folder with index.html outside of Public Folder [Rails]

So guys, I just create my swagger documentation by manually type it on swagger editor and then attach it in swagger-UI. I can call my documentation well by place it on public/documentation (where the documentation folder include my swagger.json file and swagger-ui in it). Then I call it by using localhost:3000/documentation/ and here's the result. localhost:3000/documentation

So, the point is, how do I make it protected? I mean it's not an for public consumption. I've been thinking to move it outside public folder then call it using controller. But none of them working.