Update docs (#7316)

Call main() does not returns any loop. Close #7314

docs/client_reference.rst

@@ -32,8 +32,7 @@ Usage example::
              html = await fetch(client)
              print(html)
 
-     loop = asyncio.get_event_loop()
-     loop.run_until_complete(main())
+     asyncio.run(main())
 
 
 The client session supports the context manager protocol for self closing.

docs/http_request_lifecycle.rst

@@ -77,8 +77,7 @@ So you are expected to reuse a session object and make many requests from it. Fo
                 html = await response.text()
                 print(html)
 
-    loop = asyncio.get_event_loop()
-    loop.run_until_complete(main())
+    asyncio.run(main())
 
 
 Can become this:
@@ -98,8 +97,7 @@ Can become this:
             html = await fetch(session, 'http://python.org')
             print(html)
 
-    loop = asyncio.get_event_loop()
-    loop.run_until_complete(main())
+    asyncio.run(main())
 
 On more complex code bases, you can even create a central registry to hold the session object from anywhere in the code, or a higher level ``Client`` class that holds a reference to it.
 

docs/index.rst

@@ -83,8 +83,7 @@ Client example
               html = await response.text()
               print("Body:", html[:15], "...")
 
-  loop = asyncio.get_event_loop()
-  loop.run_until_complete(main())
+  asyncio.run(main())
 
 This prints:
 

docs/web_lowlevel.rst

@@ -69,13 +69,7 @@ The following code demonstrates very trivial usage example::
        await asyncio.sleep(100*3600)
 
 
-   loop = asyncio.get_event_loop()
-
-   try:
-       loop.run_until_complete(main())
-   except KeyboardInterrupt:
-       pass
-   loop.close()
+   asyncio.run(main())
 
 
 In the snippet we have ``handler`` which returns a regular