calling a javascript function and waiting for the promise with `rusty_v8`

let result = function.call(scope, recv, &[]).expect("couldnt run");
/*i got this result which is a promise. now how do i get the value of the promise

let value = ??
*/

let result = function.call(scope, recv, &[]).expect("couldnt run");
/*i got this result which is a promise. now how do i get the value of the promise

let value = ??
*/