example: don't os.Exit unconditionally, hiding panics

Signed-off-by: Elias Naur <mail@eliasnaur.com>

example/gophers/main.go

@@ -60,10 +60,10 @@ func main() {
 			app.Size(unit.Dp(400), unit.Dp(800)),
 			app.Title("Gophers"),
 		)
-		defer os.Exit(0)
 		if err := newApp(w).run(); err != nil {
 			log.Fatal(err)
 		}
+		os.Exit(0)
 	}()
 	app.Main()
 }

example/hello/hello.go

@@ -21,11 +21,11 @@ import (
 
 func main() {
 	go func() {
-		defer os.Exit(0)
 		w := app.NewWindow()
 		if err := loop(w); err != nil {
 			log.Fatal(err)
 		}
+		os.Exit(0)
 	}()
 	app.Main()
 }

example/kitchen/kitchen.go

@@ -68,11 +68,11 @@ func main() {
 	}()
 
 	go func() {
-		defer os.Exit(0)
 		w := app.NewWindow(app.Size(unit.Dp(800), unit.Dp(700)))
 		if err := loop(w); err != nil {
 			log.Fatal(err)
 		}
+		os.Exit(0)
 	}()
 	app.Main()
 }