add Future.Then

x/async/async_go.go

@@ -34,7 +34,7 @@ func Race[T1 any](futures ...Future[T1]) Future[T1] {
 		ch := make(chan T1)
 		for _, future := range futures {
 			future := future
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				defer func() {
 					// Avoid panic when the channel is closed.
 					_ = recover()
@@ -56,7 +56,7 @@ func All[T1 any](futures ...Future[T1]) Future[[]T1] {
 		wg.Add(n)
 		for i, future := range futures {
 			i := i
-			future(func(v T1) {
+			future.Then(func(v T1) {
 				results[i] = v
 				wg.Done()
 			})