Semaphore.swift

import Cocoa

let queue = Cocoa.OperationQueue()

let sema = DispatchSemaphore.init(value: 0)

queue.addOperation {
    print("T1 Wait")

    queue.addOperation {
        sleep(5)
        print("T2 Signal")
        sema.signal()
    }

    _ = sema.wait(timeout: .distantFuture)
    print("T1 DONE")
    exit(0)
}

print("Runloop")
CFRunLoopRun()