Removed error returns from Window.Show() and Window.Hide(). Also properly locked the Window's mutex lock in both functions.

window.go

@@ -99,19 +99,17 @@ func (w *Window) Open(control Control) (err error) {
 }
 
 // Show shows the window.
-func (w *Window) Show() (err error) {
+func (w *Window) Show() {
-	err = w.sysData.show()
+	w.lock.Lock()
-	if err != nil {
+	defer w.lock.Unlock()
-		return fmt.Errorf("error showing window: %v", err)
+
-	}
+	w.sysData.show()
-	return nil
 }
 
 // Hide hides the window.
-func (w *Window) Hide() (err error) {
+func (w *Window) Hide() {
-	err = w.sysData.hide()
+	w.lock.Lock()
-	if err != nil {
+	defer w.lock.Unlock()
-		return fmt.Errorf("error hiding window: %v", err)
+
-	}
+	w.sysData.hide()
-	return nil
 }