Fix #1909: add example for middleware execution order

docs/web.rst

@@ -922,6 +922,43 @@ if user has no permissions to access the underlying resource.
 They may also render errors raised by the handler, perform some pre- or
 post-processing like handling *CORS* and so on.
 
+The following code demonstrates middlewares execution order::
+
+   from aiohttp import web
+   def test(request):
+       print('Handler function called')
+       return web.Response(text="Hello")
+
+   async def middleware1(app, handler):
+       async def middleware_handler(request):
+           print('Middleware 1 called')
+           response = await handler(request)
+           print('Middleware 1 finished')
+
+           return response
+       return middleware_handler
+
+   async def middleware2(app, handler):
+       async def middleware_handler(request):
+           print('Middleware 2 called')
+           response = await handler(request)
+           print('Middleware 2 finished')
+
+           return response
+       return middleware_handler
+
+
+   app = web.Application(middlewares=[middleware1, middleware2])
+   app.router.add_get('/', test)
+   web.run_app(app)
+
+Produced output::
+
+   Middleware 1 called
+   Middleware 2 called
+   Handler function called
+   Middleware 2 finished
+   Middleware 1 finished
 
 Example
 ^^^^^^^