From be665a35265f56273c350bed5eeb00c1a85ab457 Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@gmail.com>
Date: Sat, 9 Jun 2018 13:36:35 +0900
Subject: [PATCH] ui: Better way to avoid blocking

Fixes #625
---
 internal/ui/ui_js.go | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index 2b17c47fd..bc3b58258 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -208,16 +208,17 @@ func (u *userInterface) loop(g GraphicsContext) error {
 	var cf js.Callback
 	f = func([]js.Value) {
 		if err := u.update(g); err != nil {
-			go func() {
-				ch <- err
-				close(ch)
-			}()
+			ch <- err
+			close(ch)
 			return
 		}
 		js.Global.Get("window").Call("requestAnimationFrame", cf)
 	}
 	cf = js.NewCallback(f)
-	f(nil)
+	// Call f asyncly to be async since ch is used in f.
+	go func() {
+		f(nil)
+	}()
 	return <-ch
 }