fun doSomething() = callbackFlow{
    withContext(<http://Dispatchers.IO|Dispatchers.IO>){
        offer(Unit)
    }
}

private fun Call.downloadAndSaveTo(
			output: Sink,
			bufferSize: Long = DEFAULT_BUFFER_SIZE.toLong() * 10,
			flushSize: Long = bufferSize * 100
	)Flow<Long> = callbackFlow<Long> {
		enqueue(object : Callback {
			override fun onFailure(call: Call?, e: IOException) {
				this@callbackFlow.close(e)
			}

			override fun onResponse(call: Call?, response: Response) {
				if (!response.isSuccessful) {
					this@callbackFlow.close(IllegalStateException("Unexpected HTTP code: ${response.code()}"))
				}

				try {
					response.body()?.use { body ->
						val contentLength = body.contentLength()
						val buffer = Buffer()
						var finished = false
						var totalLength = 0L

						var lastFlush = 0L

						output.buffer().use { out ->
							body.source().use { source ->
								while (isActive) {
									val read = source.read(buffer, bufferSize)
									if (read == -1L) {
										out.flush()

										finished = true
										break
									}

									out.write(buffer, read)
									totalLength += read

									if ((totalLength - lastFlush) / flushSize > 0) {
										out.flush()
										lastFlush = totalLength
									} else
										out.emit()

									offer(read)
								}
							}
						}
					}

					channel.close()
				} catch (e: Exception) {
					this@callbackFlow.close(e)
				}
			}
		})

		awaitClose {
			// Cancel the call
			this@downloadAndSaveTo.cancel()

			// Close other resources..
		}
	}.flowOn(<http://Dispatchers.IO|Dispatchers.IO>)

awaitClose