FileUploadWorker.kt

class FileUploadWorker(context: Context, params: WorkerParameters) : Woker(context, params) {
    override fun doWork(): Result {
        return try {
            val response = ... // send PUT /message/media reequest
            when (uploadResponse.code() / 100) {
                2 -> Result.SUCCESS
                4 -> Result.FAILURE
                else -> Result.RETRY
            }
        } catch (e: FileNotFoundException) {
            Result.FAILURE
        } catch (e: IOException) {
            Result.RETRY
        } finally {
            ... // close resources
        }
    }
}