close issue of #337 (#347)

core/syncx/sharedcalls.go

@@ -70,8 +70,6 @@ func (g *sharedGroup) createCall(key string) (c *call, done bool) {
 
 func (g *sharedGroup) makeCall(c *call, key string, fn func() (interface{}, error)) {
 	defer func() {
-		// delete key first, done later. can't reverse the order, because if reverse,
-		// another Do call might wg.Wait() without get notified with wg.Done()
 		g.lock.Lock()
 		delete(g.calls, key)
 		g.lock.Unlock()