Support providing a list of Closeable to CancellableGroup construction

korio/src/commonMain/kotlin/korlibs/io/lang/Closeable.kt

@@ -93,9 +93,16 @@ fun CloseableCancellable(callback: (Throwable?) -> Unit): CloseableCancellable =
     override fun cancel(e: Throwable) = callback(e)
 }
 
-class CancellableGroup : CloseableCancellable {
+class CancellableGroup() : CloseableCancellable {
     private val cancellables = arrayListOf<Cancellable>()
 
+    constructor(vararg items: Cancellable) : this() {
+        items.fastForEach { this += it }
+    }
+    constructor(items: Iterable<Cancellable>) : this() {
+        for (it in items) this += it
+    }
+
     operator fun plusAssign(c: CloseableCancellable) {
         cancellables += c
     }

korio/src/commonTest/kotlin/korlibs/io/lang/CancellableTest.kt

@@ -0,0 +1,32 @@
+package korlibs.io.lang
+
+import kotlin.test.*
+
+class CancellableTest {
+    @Test
+    fun testCancellableGroup() {
+        val log = arrayListOf<String>()
+        val cancellable1 = Cancellable { log += "1" }
+        val cancellable2 = Cancellable { log += "2" }
+        CancellableGroup(cancellable1, cancellable2).let { group ->
+            assertEquals("", log.joinToString(","))
+            group.cancel()
+            assertEquals("1,2", log.joinToString(","))
+            log.clear()
+        }
+        CancellableGroup(listOf(cancellable1, cancellable2)).let { group ->
+            assertEquals("", log.joinToString(","))
+            group.cancel()
+            assertEquals("1,2", log.joinToString(","))
+            log.clear()
+        }
+        CancellableGroup().let { group ->
+            group.addCancellable(cancellable1)
+            group.addCancellable(cancellable2)
+            assertEquals("", log.joinToString(","))
+            group.cancel()
+            assertEquals("1,2", log.joinToString(","))
+            log.clear()
+        }
+    }
+}