A flow is a factory for subscriptions. It only does work when it's collected, and may be collected multiple times, creating independent work streams for each collector.

When you write a function that returns a Flow, that function should do no work of its own, it should only construct the Flow so that the Flow knows how to do the work when a caller collects it.

Right now your

DownloadController.download

method is doing a lot of work of its own - it is itself a

suspend

function, it's performing

launch

operations that create child jobs of the

withContext

block's scope and don't permit the

withContext

block to return until those launched jobs are complete