ASIO examples use "deprecated" `io_service`

[Martin Rueckl]

Hi Folks,
I think boost::asio::io_service got replaced by boost::asio::io_context.
At least in 1.72 io_service is only a typedef forwarding to io_context.

Maybe the examples can be modified so people learn the new stuff :)

Hth,
Martin

[Oliver Kowalke]

you are welcome to provide a patch/pull request