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kotlinlang

How can I cancel a channel.send, that is waiting in receive buffer in unlimited?

You can't remove something from a channel once it's been sent. 

You could use an unbuffered channel to force all sends to suspend on backpressure - then you could cancel sends by cancelling the coroutine performing the send (I think). Channel sends are fair, so this would still act like a queue – 5 coroutines call and suspending on send will be sent+resumed in order. 

would you do that if you were to create a sort of a downloader queue? to rely on the backpressure, keeping the Jobs in a map, and cancel them when user decides to? would work but sounds iffy

you could also create your own queue if you need other behaviors as well

no, just implement your own queue. could use channels internally but just as an implementation detail

but then the queue needs to be shared state, with sychronization etc which I wanted to avoid.. thread that blocks on BlockingQueue.take almost feels better now