To explore the Fyne toolkit further, let's build our latest version of the GoMail application designed in Chapter 4, Walk – Building Graphical Windows Applications. We will start by setting out the basic application layout.
Creating a complex layout with Fyne is a case of combining multiple containers, each of which are using one of the layouts provided. It would be possible to write our own layout to set up the interface with a single container, but for this exploration, we will use only the built-in components. Let's start by creating the main application window.
To load the first window of a Fyne application, we must create a new application instance using app.New(). After that, we can call the NewWindow() function on this application object. The returned fyne.Window object allows us to control the window on screen and to set its content:
import "fyne.io/fyne/app"
func main() {
mailApp := app.New()
browse := mailApp.NewWindow("GoMail...