Fs2

If you want to get FS2 is a streaming library for Scala which offers more lightweight and more “functional” alternative to Akka Streams. However, as it’s relatively young it either misses some functionality, or has it available in non-obvious way and lacks appropriate documentation. One such example is retrieving data from callback-based API which expects an interface with callbacks for next element, stream end and stream failure - like Subscriber from Reactive Streams Initiative.