Fix run_in_executor call in user guide

Addresses #2493.

diff --git a/docs/guide/coroutines.rst b/docs/guide/coroutines.rst
index eb500da12512ea1448d91eeffcf50af8f62d713f..29f614ccebf6c79d11c8b2319dbc1c6f611b4456 100644 (file)
--- a/docs/guide/coroutines.rst
+++ b/docs/guide/coroutines.rst
@@ -177,7 +177,7 @@ use `.IOLoop.run_in_executor`, which returns
 ``Futures`` that are compatible with coroutines::
 
     async def call_blocking():
-        await IOLoop.current().run_in_executor(blocking_func, args)
+        await IOLoop.current().run_in_executor(None, blocking_func, args)
 
 Parallelism
 ^^^^^^^^^^^