…hich is not read.

Maybe needed for mono(old version only?) and net5.0(without NETSTANDARD1_3 defined)

In Mono(with btls provider) on linux, and maybe also for apple provider, Write is called in another thread, so it will run after the call to Flush.

`try{_=task.Result;}catch(AggregateException ex){ExceptionDispatchInfo.Capture(ex.InnerException).Throw();/*unreachable*/throw;}` => `task.GetAwaiter().GetResult()`, the latter one will not wrap Exception as AggregateException.

…ix concurrent issue for Wrap