Fixes to support Asio changes (API Change):

This adjusts Beast's interfaces and implementation to match
the changes in Boost.Asio.

example/http/client/crawl/http_crawl.cpp

@@ -151,10 +151,7 @@ class worker : public std::enable_shared_from_this<worker>
 
     crawl_report& report_;
     tcp::resolver resolver_;
-    tcp::socket socket_;
-    net::steady_timer timer_;
-    net::strand<
-        net::io_context::executor_type> strand_;
+    beast::tcp_stream stream_;
     beast::flat_buffer buffer_; // (Must persist between reads)
     http::request<http::empty_body> req_;
     http::response<http::string_body> res_;
@@ -167,11 +164,8 @@ public:
         crawl_report& report,
         net::io_context& ioc)
         : report_(report)
-        , resolver_(ioc)
-        , socket_(ioc)
-        , timer_(ioc,
-            (chrono::steady_clock::time_point::max)())
-        , strand_(ioc.get_executor())
+        , resolver_(beast::make_strand(ioc))
+        , stream_(beast::make_strand(ioc))
     {
         // Set up the common fields of the request
         req_.version(11);
@@ -184,44 +178,9 @@ public:
     void
     run()
     {
-        // Run the timer. The timer is operated
-        // continuously, this simplifies the code.
-        on_timer({});
-
         do_get_host();
     }
 
-    void
-    on_timer(beast::error_code ec)
-    {
-        if(ec && ec != net::error::operation_aborted)
-        {
-            // Should never happen
-            report_.aggregate(
-            [](crawl_report& rep)
-            {
-                ++rep.timer_failures;
-            });
-            return;
-        }
-
-        // Verify that the timer really expired since the deadline may have moved.
-        if(timer_.expiry() <= chrono::steady_clock::now())
-        {
-            socket_.shutdown(tcp::socket::shutdown_both, ec);
-            socket_.close(ec);
-            return;
-        }
-
-        // Wait on the timer
-        timer_.async_wait(
-            net::bind_executor(
-                strand_,
-                beast::bind_front_handler(
-                    &worker::on_timer,
-                    shared_from_this())));
-    }
-
     void
     do_get_host()
     {
@@ -230,27 +189,19 @@ public:
 
         // nullptr means no more work
         if(! host)
-        {
-            timer_.cancel_one();
             return;
-        }
 
         // The Host HTTP field is required
         req_.set(http::field::host, host);
 
-        // Set the timer
-        timer_.expires_after(chrono::seconds(timeout));
-
         // Set up an HTTP GET request message
         // Look up the domain name
         resolver_.async_resolve(
             host,
             "http",
-            net::bind_executor(
-                strand_,
-                beast::bind_front_handler(
-                    &worker::on_resolve,
-                    shared_from_this())));
+            beast::bind_front_handler(
+                &worker::on_resolve,
+                shared_from_this()));
     }
 
     void
@@ -268,18 +219,16 @@ public:
             return do_get_host();
         }
 
-        // Set the timer
-        timer_.expires_after(chrono::seconds(timeout));
+        // Set a timeout on the operation
+        stream_.expires_after(std::chrono::seconds(10));
 
         // Make the connection on the IP address we get from a lookup
-        net::async_connect(
-            socket_,
+        beast::async_connect(
+            stream_,
             results,
-            net::bind_executor(
-                strand_,
-                beast::bind_front_handler(
-                    &worker::on_connect,
-                    shared_from_this())));
+            beast::bind_front_handler(
+                &worker::on_connect,
+                shared_from_this()));
     }
 
     void
@@ -295,18 +244,16 @@ public:
             return do_get_host();
         }
 
-        // Set the timer
-        timer_.expires_after(chrono::seconds(timeout));
+        // Set a timeout on the operation
+        stream_.expires_after(std::chrono::seconds(10));
 
         // Send the HTTP request to the remote host
         http::async_write(
-            socket_,
+            stream_,
             req_,
-            net::bind_executor(
-                strand_,
-                beast::bind_front_handler(
-                    &worker::on_write,
-                    shared_from_this())));
+            beast::bind_front_handler(
+                &worker::on_write,
+                shared_from_this()));
     }
 
     void
@@ -325,21 +272,16 @@ public:
             });
             return do_get_host();
         }
-        
-        // Set the timer
-        timer_.expires_after(chrono::seconds(timeout));
 
         // Receive the HTTP response
         res_ = {};
         http::async_read(
-            socket_,
+            stream_,
             buffer_,
             res_,
-            net::bind_executor(
-                strand_,
-                beast::bind_front_handler(
-                    &worker::on_read,
-                    shared_from_this())));
+            beast::bind_front_handler(
+                &worker::on_read,
+                shared_from_this()));
     }
 
     void
@@ -368,8 +310,8 @@ public:
         });
 
         // Gracefully close the socket
-        socket_.shutdown(tcp::socket::shutdown_both, ec);
-        socket_.close(ec);
+        stream_.socket().shutdown(tcp::socket::shutdown_both, ec);
+        stream_.close();
 
         // If we get here then the connection is closed gracefully
 
@@ -412,7 +354,7 @@ int main(int argc, char* argv[])
     auto const threads = std::max<int>(1, std::atoi(argv[1]));
 
     // The io_context is required for all I/O
-    net::io_context ioc{1};
+    net::io_context ioc;
 
     // The work keeps io_context::run from returning
     auto work = net::make_work_guard(ioc);