Why does `setTimeout` doesn't work when callback is passed via yield?

function so(){console.log(`inside the timer`)}

function* sogen()
{
    const callback = yield;

    setTimeout(callback, 2000);

    return 1;
}

function(){
    var gen = sogen();
    gen.next(so), gen.next(so);
}()

Why am I never reaching function so?

from Why does `setTimeout` doesn't work when callback is passed via yield?