add boost on mac

macx64/include/boost/asio/this_coro.hpp

@@ -0,0 +1,47 @@
+//
+// this_coro.hpp
+// ~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2019 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)
+//
+
+#ifndef BOOST_ASIO_THIS_CORO_HPP
+#define BOOST_ASIO_THIS_CORO_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/config.hpp>
+
+#include <boost/asio/detail/push_options.hpp>
+
+namespace boost {
+namespace asio {
+namespace this_coro {
+
+/// Awaitable type that returns the executor of the current coroutine.
+struct executor_t
+{
+  BOOST_ASIO_CONSTEXPR executor_t()
+  {
+  }
+};
+
+/// Awaitable object that returns the executor of the current coroutine.
+#if defined(BOOST_ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
+constexpr executor_t executor;
+#elif defined(BOOST_ASIO_MSVC)
+__declspec(selectany) executor_t executor;
+#endif
+
+} // namespace this_coro
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#endif // BOOST_ASIO_THIS_CORO_HPP