[xfer]

You can do DoXxx() using DoXxxAsync() by calling wait() on the future it returns. No duplicated code necessary.

[infogulch]

It's nice that that'll work but it's... kinda gross. Can it call wait() automatically via some auto type conversion? Ideally in a synchronous context it would call wait(), and in an async context it would automatically annotate await (and you could always override by calling wait() manually).