async: work both go and llgo

x/cbind/buf.go

@@ -0,0 +1,12 @@
+package cbind
+
+import "unsafe"
+
+type slice struct {
+	data unsafe.Pointer
+	len  int
+}
+
+func GoBytes(buf *int8, n int) []byte {
+	return *(*[]byte)(unsafe.Pointer(&slice{unsafe.Pointer(buf), n}))
+}