Show onboarding during first launch

MainViewWithOnboarding.swift

import SwiftUI

struct MainView: View {
    @EnvironmentObject var nav: NavigationController
    var body: some View {
        ZStack {
            if nav.hasSeenOnboarding {
                MainContentView()
            }else {
                OnboardingView()
            }
        }
    }
}

struct OnboardingView: View {
    @EnvironmentObject var nav: NavigationController
    var body: some View {
        VStack(spacing: 20) {
            Text("Onboarding").font(.title)
            Text("Show all the information")
            
            Button(action: {
                self.nav.hasSeenOnboarding = true
            }) {
                Text("done")
            }
        }
    }
}

struct MainContentView: View {
    var body: some View {
        Text("Main content view")
    }
}