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I'm trying to track down the source of a `JobCancellationException`. My crash reporting tool isn't offering any useful information, and I don't quite understand this exception..

```kotlinx.coroutines.JobCancellationException · Job was cancelled
unknown fileunknown method```

Looking at the breadcrumbs, it looks like this occurs after `MainActivity.onDestroy()` is called in my Android app. So presumably, someone is swiping the app away from recents (potentially killing the app process)

There's a coroutine that runs when the app is launched, which I suspect is the source. The scope used to launch this coroutine is:

```CoroutineScope(Dispatchers.Main + job + coroutineExceptionHandler)```
Where:
 `job` is a `SupervisorJob`, and
`coroutineExceptionHandler` is an instance of `CoroutineExceptionHandler` that logs errors

I'm not sure if I'm looking in the wrong place, or the app is throwing an exception that is swallowed by coroutines, or the 'crash' is simply that the job is being cancelled. Any insight would be great, I'm still wrapping my head around JobCancellationExceptions and CoroutineExceptionHandlers

Turning on debug mode should help, because it enables stacktrace in JCE

Thanks for the quick reply. The issue here is, I'm not able to reproduce this crash myself

~Oh, I wonder if I can ship the app (it's only in alpha) with debug mode on.. Would that be crazy?~

Just had a read of <https://github.com/Kotlin/kotlinx.coroutines/blob/master/docs/debugging.md>

Thanks

<@US7DACDEH> Are you using `Channel` and the `offer` function?

<@US7DACDEH>
Then it's quite likely you have these exceptions thrown here either:
• because you're using `consume`, `consumeEach` or `consumeAsFlow()` when, respectively, you should not, when you should use a plain `for` loop or `receive()`, or when you should use `receiveAsFlow()` 
• because you have a race condition, for example in `callbackFlow`/`channelFlow` or elsewhere, which is this issue: <https://github.com/Kotlin/kotlinx.coroutines/issues/974>
• because you `close` or `cancel` the channel in a way or another, where a `JobCancellationException` is passed as a cause.