basic_stream dtor cannot throw

fix #1688

include/boost/beast/core/impl/basic_stream.hpp

@@ -145,9 +145,13 @@ basic_stream<Protocol, Executor, RatePolicy>::
 impl_type::
 close()
 {
-    socket.close();
+    {
+        error_code ec;
+        socket.close(ec);
+    }
     timer.cancel();
 
+
     // have to let the read/write ops cancel the timer,
     // otherwise we will get error::timeout on close when
     // we actually want net::error::operation_aborted.