public MainContext async_context { construct; get; }

The MainContext that miscellaneous session-related asynchronous callbacks are invoked on.

(Eg, setting idle_timeout will add a timeout source on this context.)

For a plain Session, this property is always set to the MainContext that is the thread-default at the time the session was created, and cannot be overridden. For the deprecated Session subclasses, the default value is null, meaning to use the global default MainContext.

If use_thread_context is false, this context will also be used for asynchronous HTTP I/O.