New to swift, Having trouble with TabView

Code Block swift
struct ContentView: View {
    /*
     This "tabSelection" variable is used by the TabView to
     update which tab is currently selected. This value will
     correspond to the value of the ".tag" modifer on each
     view of the TabView.
     The "@State" property wrapper is needed so that SwiftUI
     can update the value of this variable.
     */
    @State
    private var tabSelection = 0
   
    var body: some View {
        TabView(selection: $tabSelection) {
            FirstTabView()
                .tabItem {
                    /*
                     The ".tabItem" modifier is used to set
                      the contents of the button on the tab bar.
                     This view will accept an optional Image and/or Text view.
                     */
                    Image(systemName: "1.square.fill")
                    Text("Tab Label 1")
                }
                .tag(0) /* When this tab is selected, tabSelection will update with this value */          
            SecondTabView()
                .tabItem {
                    Image(systemName: "2.square.fill")
                    Text("Tab Label 2")
                }
                .tag(1)
        }
    }
}
struct FirstTabView: View {
    var body: some View {
        /*
         This is where you would create the content of your view inside
         each tab. Other views, functions, etc.
         */
        NavigationView {
            Text("First Tab View Body")
                .navigationTitle("First")
        }
    }
}
struct SecondTabView: View {
    var body: some View {
        NavigationView {
            Text("Second Tab View Body")
                .navigationTitle("Second")
        }
    }
}