import Dispatch enum FetchError: Error { case bad } func fetch(_ ok: Bool) async throws -> Int { if !ok { throw FetchError.bad } return 42 } print("Start") let sem = DispatchSemaphore(value: 0) Task { do { let v = try await fetch(false) print("ok \(v)") } catch { print("error") } sem.signal() } sem.wait() print("Done")