Setup sigleton pattern in Kotlin.

NewsAppModel.kt

class NewsAppModel {
    companion object {
        private var INSTANCE: NewsAppModel? = null
        fun getInstance(): NewsAppModel {
            if (INSTANCE == null) {
                INSTANCE = NewsAppModel()
            }

            val i = INSTANCE
            return i!!
        }
    }

    private constructor() {
        EventBus.getDefault().register(this)
    }
    
}