I am running this code

fun test1() {
    println("1")
    printId()
    thread {
        println("2")
        printId()
        throw IllegalStateException("an exception")
    }.join()
    println("3")
}


fun printId(){
    println("Thread ID: $id")
}

val id get() = Thread.currentThread().id

and getting

1
Thread ID: 1
2
Thread ID: 11
Exception in thread "Thread-0" java.lang.IllegalStateException: an exception
	at com.github.andrewgazelka.kotlintest.ThreadExceptionTestKt$test1$1.invoke(ThreadExceptionTest.kt:12)
	at com.github.andrewgazelka.kotlintest.ThreadExceptionTestKt$test1$1.invoke(ThreadExceptionTest.kt)
	at kotlin.concurrent.ThreadsKt$thread$thread$1.run(Thread.kt:30)
3

why

Thread-0

?

Hi Andrew, did you figure it out?

yes @Systemkern look at the next comment