Using https://github.com/JakeWharton/retrofit2-kotlin-coroutines-adapter

repository.kt

async(UI) {
    // before using https://github.com/JakeWharton/retrofit2-kotlin-coroutines-adapter
    val call: Call<ApiResponse<List<VideoExtra>>> = service.getVideoExtras(userId)
    val response: Response<ApiResponse<List<VideoExtra>>> = bg { call.execute() }.await()
    
    // When using it, our code looks much better
    val deferred: Deferred<Response<ApiResponse<List<VideoExtra>>>> = service.getVideoExtras(userId)
    val response: Response<ApiResponse<List<VideoExtra>>> = deferred.await()
    // using the response's data to set the value of LiveData(), etc...
}