Capture port by value to prevent dangling reference.

asio/src/examples/cpp17/coroutines_ts/chat_server.cpp

@@ -204,7 +204,10 @@ int main(int argc, char* argv[])
     {
       unsigned short port = std::atoi(argv[i]);
       co_spawn(io_context,
-          [&]{ return listener(tcp::acceptor(io_context, {tcp::v4(), port})); },
+          [&io_context, port]
+          {
+            return listener(tcp::acceptor(io_context, {tcp::v4(), port}));
+          },
           detached);
     }