ThreadPoolExecutor kill will wait_for_termination in JRuby

Author: bensheldon

lib/concurrent-ruby/concurrent/executor/java_executor_service.rb

@@ -46,8 +46,9 @@ def shutdown
       def kill
         synchronize do
           @executor.shutdownNow
-          nil
         end
+        wait_for_termination
+        nil
       end
 
       private