when the context shuts down cleanly, we'd like to shutdown our async handler threads, too

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/AsyncHandler.java

@@ -231,4 +231,8 @@ private void processAsyncActions() {
             }
         }
     }
+
+    public void shutdown() {
+        executorService.shutdownNow();
+    }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PythonContext.java

@@ -288,6 +288,7 @@ public void deregisterShutdownHook(Object callable) {
 
     @TruffleBoundary
     public void runShutdownHooks() {
+        handler.shutdown();
         for (CallTarget f : atExitHooks.values()) {
             f.call();
         }