Little change of session API + Update examples

Former-commit-id: e8c58b186acf1c8932af6e886dae7035f4d581c1

_examples/sessions/securecookie/main.go

@@ -62,10 +62,16 @@ func newApp() *iris.Application {
 		mySessions.Start(ctx).Clear()
 	})
 
+	app.Get("/update", func(ctx context.Context) {
+		// updates expire date with a new date
+		mySessions.ShiftExpiraton(ctx)
+	})
+
 	app.Get("/destroy", func(ctx context.Context) {
 		//destroy, removes the entire session data and cookie
 		mySessions.Destroy(ctx)
-	}) // Note about destroy:
+	})
+	// Note about destroy:
 	//
 	// You can destroy a session outside of a handler too, using the:
 	// mySessions.DestroyByID