gistfile1.txt

@State private var progress: Double = 0
@State private var showError: Bool = false

// ...

.task {
    do {
        for try await percentage in DownloadAPI.downloadStream() {
            progress = percentage
        }
    } catch {
        self.showError = true
    }
}
.alert("Download Error", isPresented: $showError) {
    Button("OK", role: .cancel) { }
}