Fix compilation error with boost 1.71

get_io_service() is a deprecated function and should be replaced with get_executor().

Look it up on:
https://www.boost.org/doc/libs/1_67_0/doc/html/boost_asio/reference/ip__tcp/acceptor.html

daemon/src/main.cpp

@@ -17,9 +17,9 @@ private:
   char data[max_length];
 public:
   typedef boost::shared_ptr<con_handler> pointer;
-  con_handler(boost::asio::io_service& io_service): sock(io_service){}
+  con_handler(boost::asio::basic_socket_acceptor<boost::asio::ip::tcp>::executor_type& io_service): sock(io_service){}
 
-  static pointer create(boost::asio::io_service& io_service) {
+  static pointer create(boost::asio::basic_socket_acceptor<boost::asio::ip::tcp>::executor_type& io_service) {
     return pointer(new con_handler(io_service));
   }
 
@@ -55,7 +55,8 @@ class Server {
 private:
    tcp::acceptor acceptor_;
    void start_accept() {
-     con_handler::pointer connection = con_handler::create(acceptor_.get_io_service());
+     auto executor = acceptor_.get_executor();
+     con_handler::pointer connection = con_handler::create(executor);
      acceptor_.async_accept(connection->socket(), boost::bind(&Server::handle_accept, this, connection,
         boost::asio::placeholders::error));
   }