Have ui.Go() return on main() return on Unix.

gtkcalls_unix.go

@@ -32,6 +32,10 @@ func gtk_main() {
 	C.gtk_main()
 }
 
+func gtk_main_quit() {
+	C.gtk_main_quit()
+}
+
 func gtk_window_new() *gtkWidget {
 	// 0 == GTK_WINDOW_TOPLEVEL (the only other type, _POPUP, should not be used)
 	return fromgtkwidget(C.gtk_window_new(0))

uitask_unix.go

@@ -28,7 +28,10 @@ func ui(main func()) error {
 		return true	// don't destroy the callback
 	})
 
-	go main()
+	go func() {
+		main()
+		uitask <- gtk_main_quit
+	}()
 
 	gtk_main()
 	return nil