inline fun <T, R> Flow<T>.concurrentMap(
    concurrency: Int,
    @BuilderInference crossinline block: suspend (T) -> R
) = flow<R> {
    val scope = CoroutineScope(Executors.newFixedThreadPool(concurrency).asCoroutineDispatcher())
    val deferredResults = mutableListOf<Deferred<R>>()
    collect { value ->
        deferredResults.add(scope.async { block(value) })
    }
    deferredResults.awaitAll().forEach { newValue -> emit(newValue) }
    scope.cancel()
}

flatMapMerge