Keep running the timer in the background at swiftUI

I want a timer to keep going while in the background.

Here is current code for the timer:

struct ContentView: View {
@State var timeRemaining = 10
let timer = Timer.publish(every: 1, on: .main, in: .common).autoconnect()

var body: some View {
    Text("\(timeRemaining)")
        .onReceive(timer) { _ in
            if self.timeRemaining > 0 {
                self.timeRemaining -= 1
            }
        }
} }

How can I make it keep going in the background?