Add Await, which allows Go to wait for Javascript promises

utils/utils.go

@@ -71,3 +71,32 @@ func CreatePromise(f PromiseFn) interface{} {
 	// Create and return the Promise object
 	return Promise.New(handler)
 }
+
+// Await waits on a Javascript value. It returns the results of the then and
+// catch functions once it resolves.
+func Await(awaitable js.Value) ([]js.Value, []js.Value) {
+	then := make(chan []js.Value)
+	defer close(then)
+	thenFunc := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		then <- args
+		return nil
+	})
+	defer thenFunc.Release()
+
+	catch := make(chan []js.Value)
+	defer close(catch)
+	catchFunc := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		catch <- args
+		return nil
+	})
+	defer catchFunc.Release()
+
+	awaitable.Call("then", thenFunc).Call("catch", catchFunc)
+
+	select {
+	case result := <-then:
+		return result, nil
+	case err := <-catch:
+		return nil, err
+	}
+}