withoutAnyCancellable.swift

let stream = Publishers.Just("is Alive?")
    .delay(for: .seconds(5), scheduler: RunLoop.main)
    .sink(receiveCompletion: { (completion) in
        switch completion {
        case .finished: print("finished")
        case .failure(let error): print(error)
        }
    }, receiveValue: {
        print($0)
    })

DispatchQueue.main.asyncAfter(deadline: .now() + 3) {
    UIApplication.shared.keyWindow?.rootViewController = nil
}

<Output>
viewController deinit
is Alive?
finished