(Go) Async Task Chain

Demonstrates how to combine a sequence of asynchronous tasks into a single task chain to be run in a background thread.

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    //  All Chilkat classes can be unlocked at once at the beginning of a program
    //  by calling UnlockBundle.  It requires a Bundle unlock code.
    chilkatGlob := NewGlobal()
    success := chilkatGlob.UnlockBundle("Anything for 30-day trial.")
    if success != true {
        fmt.Println(chilkatGlob.LastErrorText())
        return
    }

    mailman := NewMailMan()

    //  Set the POP3 server's hostname
    mailman.MailHost = "pop.someMailServer.com"

    //  Set the POP3 login/password and any other requirements..
    mailman.PopUsername = "myLogin"
    mailman.PopPassword = "myPassword"
    mailman.PopSsl = true
    mailman.MailPort = 995

    //  Connect to the POP3 server:
    success = mailman.Pop3BeginSession()
    if !success {
        fmt.Println(mailman.LastErrorText())
        return
    }

    //  Get the number of messages in the mailbox.
    numMessages := mailman.GetMailboxCount()
    if numMessages == 0 {
        fmt.Println("No email messages in the POP3 mailbox.")
        return
    }

    taskChain := NewTaskChain()

    //  Create async task objects to fetch each email message
    //  by its sequence number
    var i int
    var task  Task

    for i = 1; i <= numMessages; i++ {

        task = mailman.FetchByMsgnumAsync(i)
        if task == nil  {
            fmt.Println(mailman.LastErrorText())
            return
        }

        //  Append each task to the task chain.
        success = taskChain.Append(task)
        if !success {
            fmt.Println(taskChain.LastErrorText())
            return
        }

        task.DisposeTask()

    }

    //  At this point, no tasks have actually started running.
    //  All we've done so far is to create tasks for the work that will be done
    //  when the task chain is run.

    //  Start the task chain running in a background thread.
    //  Each task is run one after the other (on the same background thread) until all tasks have completed.
    //  The task chain will stop at the first task that fails.
    taskChain.StopOnFailedTask = true
    success = taskChain.Run()
    if !success {
        fmt.Println(taskChain.LastErrorText())
        return
    }

    //  The application is now free to do anything else
    //  while the emails are being downloaded

    //  For this example, we'll simply sleep and periodically
    //  check to see if the taskchain if finished.
    for taskChain.Finished() != true {

        //  Sleep 100 ms.
        taskChain.SleepMs(100)

    }

    //  A finished task chain could be one that was canceled, aborted, or truly finished.

    //  If the task chain "completed", then it ran to completion.  A "completed" task will
    //  have a StatusInt equal to 7.   If the task finished, but was not completed, then it must've
    //  been aborted or canceled:
    if taskChain.StatusInt() != 7 {
        fmt.Println("Task did not complete.")
        fmt.Println("task chain status: ", taskChain.Status())
        return
    }

    email := NewEmail()

    numTasks := taskChain.NumTasks()
    taskIdx := 0

    for (taskIdx < numTasks) {

        task = taskChain.GetTask(taskIdx)

        //  Load the email object with email downloaded by this task.
        success = email.LoadTaskResult(task)
        if !success {
            fmt.Println("Failed to load email object for task.")
        }
        else {
            fmt.Println(email.From(), "; ", email.Subject())
        }

        task.DisposeTask()

        taskIdx = taskIdx + 1
    }