Exception handling with async coroutine

asyncCoroutineExceptionHandling.kt

async(parentJob + UI) {
        val task = async(parentJob + CommonPool) {
            RestClient.apiDefinition.listPosts().execute()
        }

        val result = task.await()
        val numberOfPosts = "number of posts ${result.body()?.size}"
        numberOfPostsTextView.text = numberOfPosts

    }.invokeOnCompletion { it: Throwable? ->
        alertWithOkButton("Caught an exception inside invoke on completion callback")
        it?.printStackTrace()
    }