CLMonitor singleton to workaround the “Monitor named is already in use” exception

If you attempt to init another instance of CLMonitor with the same name it crashes with:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Monitor named SampleMonitor is already in use'

Since I wanted to use the same monitor from different tasks I needed to turn it into a singleton and came up with this:

extension CLMonitor {
    @MainActor
    static var sampleMonitor: CLMonitor {
        get async {
            @MainActor
            struct Static {
                static var task: Task<CLMonitor, Never>?
            }
            if let task = Static.task {
                return await task.value
            }
            let task = Task { await CLMonitor("SampleMonitor") }
            Static.task = task
            return await task.value
        }
    }
}

This allows this kind of thing to work without crashing:

@main
struct LocationMonitorSampleApp: App {
    
    var body: some Scene {
        WindowGroup {
            Group {
                ContentView()
                    .task {
                        let monitor = await CLMonitor.sampleMonitor
                    }
                    .task {
                        let monitor = await CLMonitor.sampleMonitor
                    }
            }
        }
    }
}

Note you can only subscribe to the events stream from one task, however the singleton means at least you can now add new regions to monitor from different tasks.