In general, the application is responsible for choosing the Io
implementation and library code should accept an Io parameter rather than
accessing this declaration. Most code should avoid referencing this
declaration entirely.
However, in some cases such as debugging, it is desirable to hardcode a
reference to this Io implementation.
This instance does not support concurrency or cancelation.
pub const global_single_threaded: *Threaded = &global_single_threaded_instance
pub const global_single_threaded: *Threaded = &global_single_threaded_instance