awaitable examples.

Closes #2104.

doc/qbk/02_examples/_examples.qbk

@@ -40,6 +40,10 @@ used to evaluate robustness. All asynchronous clients support timeouts.
         [HTTP, coroutine]
         [[path_link example/http/client/coro/http_client_coro.cpp http_client_coro.cpp]]
         [[path_link example/http/client/coro-ssl/http_client_coro_ssl.cpp http_client_coro_ssl.cpp]]
+][
+        [WebSocket, C++20 coroutine]
+        [[path_link example/http/client/awaitable/http_client_awaitable.cpp http_client_awaitable.cpp]]
+        []
 ][
         [HTTP crawl (asynchronous)]
         [[path_link example/http/client/crawl/http_crawl.cpp http_crawl.cpp]]
@@ -72,6 +76,10 @@ before disconnecting. All asynchronous clients support timeouts.
         [WebSocket, coroutine]
         [[path_link example/websocket/client/coro/websocket_client_coro.cpp websocket_client_coro.cpp]]
         [[path_link example/websocket/client/coro-ssl/websocket_client_coro_ssl.cpp websocket_client_coro_ssl.cpp]]
+][
+        [WebSocket, C++20 coroutine]
+        [[path_link example/websocket/client/awaitable/websocket_client_awaitable.cpp websocket_client_awaitable.cpp]]
+        []
 ]]
 
 [endsect]
@@ -101,6 +109,9 @@ command line. All asynchronous servers support timeouts.
         [HTTP, stackless coroutine]
         [[path_link example/http/server/stackless/http_server_stackless.cpp http_server_stackless.cpp]]
         [[path_link example/http/server/stackless-ssl/http_server_stackless_ssl.cpp http_server_stackless_ssl.cpp]]
+][
+        [HTTP, C++ 20 coroutine]
+        [[path_link example/http/server/awaitable/http_server_awaitable.cpp http_server_awaitable.cpp]]
 ][
         [HTTP, fast (optimized for speed)]
         [[path_link example/http/server/fast/http_server_fast.cpp http_server_fast.cpp]]
@@ -137,6 +148,10 @@ support timeouts.
         [WebSocket, stackless coroutine]
         [[path_link example/websocket/server/stackless/websocket_server_stackless.cpp websocket_server_stackless.cpp]]
         [[path_link example/websocket/server/stackless-ssl/websocket_server_stackless_ssl.cpp websocket_server_stackless_ssl.cpp]]
+][
+        [HTTP, C++ 20 coroutine]
+        [[path_link example/websocket/server/awaitable/websocket_server_awaitable.cpp websocket_server_awaitable.cpp]]
+        []
 ][
         [WebSocket, fast (suited for benchmarks)]
         [[path_link example/websocket/server/fast/websocket_server_fast.cpp websocket_server_fast.cpp]]
@@ -178,6 +193,19 @@ and illustrate the implementation of advanced features.
         ]]
         [[path_link example/advanced/server-flex/advanced_server_flex.cpp advanced_server_flex.cpp]]
 ][
+         [Advanced, flex (plain + SSL) with awaitable]
+         [[itemized_list
+             [Timeouts]
+             [Multi-threaded]
+             [HTTP pipelining]
+             [Parser-oriented HTTP reading]
+             [Dual protocols: HTTP and WebSocket]
+             [Flexible ports: plain and SSL on the same port]
+             [Clean exit via SIGINT (CTRL+C) or SIGTERM (kill)]
+             [Usage of cancellation_signals]
+         ]]
+         [[path_link example/advanced/server-flex-awaitable/advanced_server_flex_awaitable.cpp advanced_server_flex_awaitable.cpp]]
+ ][
         [Chat Server, multi-threaded]
         [[itemized_list
             [Multi-threaded]

example/advanced/CMakeLists.txt

@@ -9,3 +9,4 @@
 
 add_subdirectory (server)
 add_subdirectory (server-flex)
+add_subdirectory (server-flex-awaitable)

example/advanced/Jamfile

@@ -11,3 +11,6 @@ build-project server ;
 
 # SSL
 build-project server-flex ;
+
+# C++20
+build-project server-flex-awaitable ;

example/advanced/server-flex-awaitable/CMakeLists.txt

@@ -0,0 +1,31 @@
+#
+# Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail 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)
+#
+# Official repository: https://github.com/boostorg/beast
+#
+
+if (OPENSSL_FOUND)
+    GroupSources(include/boost/beast beast)
+    GroupSources(example/common common)
+    GroupSources(example/advanced/server-flex-awaitable "/")
+
+    add_executable (advanced-server-flex-awaitable
+        ${BOOST_BEAST_FILES}
+        ${PROJECT_SOURCE_DIR}/example/common/server_certificate.hpp
+        Jamfile
+            advanced_server_flex_awaitable.cpp
+    )
+
+    set_property(TARGET advanced-server-flex-awaitable PROPERTY FOLDER "example-advanced-server")
+
+    target_link_libraries (advanced-server-flex-awaitable
+        OpenSSL::SSL OpenSSL::Crypto
+        lib-asio
+        lib-asio-ssl
+        lib-beast
+        )
+
+endif()

example/advanced/server-flex-awaitable/Jamfile

@@ -0,0 +1,22 @@
+#
+# Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail 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)
+#
+# Official repository: https://github.com/boostorg/beast
+#
+
+import ac ;
+
+project
+    : requirements
+        [ ac.check-library /boost/beast//lib-asio-ssl : <library>/boost/beast//lib-asio-ssl/<link>static : <build>no ]
+    ;
+
+exe advanced-server-flex-awaitable :
+    advanced_server_flex_awaitable.cpp
+    :
+    <variant>coverage:<build>no
+    <variant>ubasan:<build>no
+    ;