template< class CloseHandler> void-or-deduced async_close( close_reason const& cr, CloseHandler&& handler);
This function is used to asynchronously send a close frame on the stream. This function call always returns immediately. The asynchronous operation will continue until one of the following conditions is true:
This operation is implemented in terms of one or more calls to the next
functions, and is known as a composed operation. The
program must ensure that the stream performs no other write operations
stream::async_close) until this operation
If the close reason specifies a close code other than beast::websocket::close_code::none, the close frame is sent with the close code and optional reason string. Otherwise, the close frame is sent with no payload.
Callers should not attempt to write WebSocket data after initiating the close. Instead, callers should continue reading until an error occurs. A read returning error::closed indicates a successful connection closure.
The reason for the close.
The handler to be called when the close operation completes. Copies will be made of the handler as required. The function signature of the handler must be:
void handler( error_code const& error // Result of operation );
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
Invocation of the handler will be performed in a manner equivalent