avoid deprecated IOLoop.current() call without running loop

README.rst

@@ -20,7 +20,8 @@ Here is a simple "Hello, world" example web app for Tornado:
 
 .. code-block:: python
 
-    import tornado.ioloop
+    import asyncio
+
     import tornado.web
 
     class MainHandler(tornado.web.RequestHandler):
@@ -32,10 +33,13 @@ Here is a simple "Hello, world" example web app for Tornado:
             (r"/", MainHandler),
         ])
 
-    if __name__ == "__main__":
+    async def main():
         app = make_app()
         app.listen(8888)
-        tornado.ioloop.IOLoop.current().start()
+        await asyncio.Event().wait()
+
+    if __name__ == "__main__":
+        asyncio.run(main())
 
 This example does not use any of Tornado's asynchronous features; for
 that see this `simple chat room

docs/guide/running.rst

@@ -8,10 +8,16 @@ configuring a WSGI container to find your application, you write a
 
 .. testcode::
 
-    def main():
+    import asyncio
+
+    async def amain():
         app = make_app()
         app.listen(8888)
-        IOLoop.current().start()
+        await asyncio.Event().wait()
+
+
+    def main():
+        asyncio.run(amain())
 
     if __name__ == '__main__':
         main()

docs/guide/structure.rst

@@ -16,7 +16,8 @@ A minimal "hello world" example looks something like this:
 
 .. testcode::
 
-    import tornado.ioloop
+    import asyncio
+
     import tornado.web
 
     class MainHandler(tornado.web.RequestHandler):
@@ -28,10 +29,13 @@ A minimal "hello world" example looks something like this:
             (r"/", MainHandler),
         ])
 
-    if __name__ == "__main__":
+    async def main():
         app = make_app()
         app.listen(8888)
-        tornado.ioloop.IOLoop.current().start()
+        await asyncio.Event().wait()
+
+    if __name__ == "__main__":
+        asyncio.run(main())
 
 .. testoutput::
    :hide:

docs/index.rst

@@ -31,7 +31,8 @@ Hello, world
 
 Here is a simple "Hello, world" example web app for Tornado::
 
-    import tornado.ioloop
+    import asyncio
+
     import tornado.web
 
     class MainHandler(tornado.web.RequestHandler):
@@ -43,10 +44,13 @@ Here is a simple "Hello, world" example web app for Tornado::
             (r"/", MainHandler),
         ])
 
-    if __name__ == "__main__":
+    async def main():
         app = make_app()
         app.listen(8888)
-        tornado.ioloop.IOLoop.current().start()
+        await asyncio.Event().wait()
+
+    if __name__ == "__main__":
+        asyncio.run(main())
 
 This example does not use any of Tornado's asynchronous features; for
 that see this `simple chat room