[toast0]

I would imagine doA() should do@ and return the result, but startA() would start it.

If you just need to wait for both to finish, something like this should do it:

   var t1 = startA();
   var t2 = startB();
   var a = finishA(t1);
   var b = finishB(t2);

finishX would naturally block until X is done.