Add cancel_after example.

doc/examples.qbk

@@ -532,7 +532,8 @@ Coroutines.
 * [@boost_asio/example/cpp20/coroutines/echo_server_with_deferred_default.cpp]
 * [@boost_asio/example/cpp20/coroutines/refactored_echo_server.cpp]
 * [@boost_asio/example/cpp20/coroutines/chat_server.cpp]
-* [@boost_asio/example/cpp20/coroutines/timeout.cpp]
+* [@boost_asio/example/cpp20/coroutines/timeout_cancel_after.cpp]
+* [@boost_asio/example/cpp20/coroutines/timeout_watchdog.cpp]
 
 
 [heading Invocation]

example/cpp20/coroutines/Jamfile.v2

@@ -37,4 +37,5 @@ exe echo_server_with_default : echo_server_with_default.cpp ;
 exe echo_server_with_deferred : echo_server_with_deferred.cpp ;
 exe echo_server_with_deferred_default : echo_server_with_deferred_default.cpp ;
 exe refactored_echo_server : refactored_echo_server.cpp ;
-exe timeout : timeout.cpp ;
+exe timeout_cancel_after : timeout_cancel_after.cpp ;
+exe timeout_watchdog : timeout_watchdog.cpp ;

example/cpp20/coroutines/timeout_cancel_after.cpp

@@ -0,0 +1,44 @@
+//
+// timeout_cancel_after.cpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2026 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#include <boost/asio.hpp>
+
+using namespace boost::asio;
+using ip::tcp;
+using namespace std::literals::chrono_literals;
+
+awaitable<void> echo(tcp::socket sock)
+{
+  char data[4196];
+  for (;;)
+  {
+    auto n = co_await sock.async_read_some(buffer(data), cancel_after(10s));
+    co_await async_write(sock, buffer(data, n), cancel_after(10s));
+  }
+}
+
+awaitable<void> listen(tcp::acceptor& acceptor)
+{
+  for (;;)
+  {
+    co_spawn(
+        acceptor.get_executor(),
+        echo(co_await acceptor.async_accept()),
+        detached);
+  }
+}
+
+int main()
+{
+  io_context ctx;
+  tcp::acceptor acceptor(ctx, {tcp::v4(), 54321});
+  co_spawn(ctx, listen(acceptor), detached);
+  ctx.run();
+}

example/cpp20/coroutines/timeout_watchdog.cpp

@@ -1,6 +1,6 @@
 //
-// timeout.cpp
-// ~~~~~~~~~~~
+// timeout_watchdog.cpp
+// ~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2026 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 //