Ionic @import css file having custom font @font-face does not work in signed apk

I have used @import in my style.css. It works well when we create apk in debug mode.

But When a signed apk is created ionic build --release android for release then this import does not works.

Css files having custom @font-face (font files including) does not work elsewhere root folder.

I have to put all css files in index.html to make it work.