https://stackoverflow.com/a/60359809/1271826

TimerTest.swift

import SwiftUI
import Combine

struct TimerTest: View {
    @State var date = Date()
    @State var showSubView = false
    @State var timer: AnyCancellable? = nil

    var body: some View {
        ZStack {
            if showSubView {
                VStack {
                    Text(" Timer Stoped?")
                    Button("Back") {
                        self.showSubView = false
                    }
                }
            }
            else {
                VStack {
                    Button("Switch to subview"){
                        self.showSubView = true
                    }

                    Text("date: \(date)")
                        .onAppear {
                            self.timer = Timer.publish(every: 1, on: .main, in: .common)
                                .autoconnect()
                                .sink { _ in
                                    print("tick", Date())
                            }
                        }
                        .onDisappear {
                            self.timer?.cancel()
                            NSLog("🔶 onDisappear stop timer")
                            // But if I close window, this method never be called
                        }
                }
            }
        }
        .frame(width: 500, height: 300)
    }
}