async_exception.nim

import asyncdispatch, math

randomize()

proc r1() {.async.} =
    echo("r1 going to sleep....")
    await sleepAsync(random(1000) + 500)
    if true:
        raise newException(ValueError, "Oops!")
    echo("r1 is awake.")

proc r2() {.async.} =
    echo("r2 entry")
    try:
        await r1()
    except ValueError:
        echo("r1 raised an exception!!!!")
    echo("r2 return")

waitFor(r2())
echo("Done.")

# ========= Output =========
# r2 entry
# r1 going to sleep....
# r1 raised an exception!!!!
# r2 return
# Traceback (most recent call last)
# async.nim(20)            async
# asyncdispatch.nim(1378)  waitFor
# asyncdispatch.nim(911)   poll
# asyncdispatch.nim(319)   processTimers
# asyncdispatch.nim(195)   complete
# asyncdispatch.nim(1082)  cb
# SIGSEGV: Illegal storage access. (Try to compile with -d:useSysAssert -d:useGcAssert for details.)