fix DeprecationWarning (#6749)

Author: chiboreache

README.rst

@@ -71,8 +71,7 @@ To get something from the web:
               html = await response.text()
               print("Body:", html[:15], "...")
 
-  loop = asyncio.get_event_loop()
-  loop.run_until_complete(main())
+    asyncio.run(main())
 
 This prints: