(Go) SMTP over Multiple Hop SSH

Demonstrates how to send email (using TCP or TLS) tunneled through mulitple-hop SSH. The scheme looks like this:

Application => ServerSSH1 => ServerSSH2 => SmtpServer

The ConnectThroughSsh and UseSsh methods are added in Chilkat version 9.5.0.55 to accomplish this task.

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    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    ssh1 := chilkat.NewSsh()

    // Connect directly to the 1st SSH server.
    success := ssh1.Connect("serverssh1.com",22)
    if success != true {
        fmt.Println(ssh1.LastErrorText())
        ssh1.DisposeSsh()
        return
    }

    // Authenticate using login/password:
    success = ssh1.AuthenticatePw("ssh1Login","ssh1Password")
    if success != true {
        fmt.Println(ssh1.LastErrorText())
        ssh1.DisposeSsh()
        return
    }

    // Connect through the 1st SSH connection to reach a 2nd SSH server.
    // Note: Any number of SSH connections may be simultaneously tunneled through a single
    // existing SSH connection.
    ssh2 := chilkat.NewSsh()
    success = ssh2.ConnectThroughSsh(ssh1,"serverssh2.com",22)
    if success != true {
        fmt.Println(ssh2.LastErrorText())
        ssh1.DisposeSsh()
        ssh2.DisposeSsh()
        return
    }

    // Authenticate with ssh2...
    success = ssh2.AuthenticatePw("ssh2Login","ssh2Password")
    if success != true {
        fmt.Println(ssh2.LastErrorText())
        ssh1.DisposeSsh()
        ssh2.DisposeSsh()
        return
    }

    mailman := chilkat.NewMailMan()

    // Tell the mailman object to connect to the SMTP server though the ssh2 tunnel (which itself is routed through ssh1).
    // The connection looks like this:  Application => ServerSSH1 => ServerSSH2 => SMTPServer
    success = mailman.UseSsh(ssh2)
    if success != true {
        fmt.Println(mailman.LastErrorText())
        ssh1.DisposeSsh()
        ssh2.DisposeSsh()
        mailman.DisposeMailMan()
        return
    }

    // Set the SMTP server.
    mailman.SetSmtpHost("smtp.someserver.com")

    // Set the SMTP login/password (if required)
    mailman.SetSmtpUsername("myUsername")
    mailman.SetSmtpPassword("myPassword")

    // Create a new email object
    email := chilkat.NewEmail()

    email.SetSubject("This is a test")
    email.SetBody("This is a test")
    email.SetFrom("Chilkat Support <support@chilkatsoft.com>")
    success = email.AddTo("Chilkat Admin","admin@chilkatsoft.com")

    success = mailman.SendEmail(email)
    if success != true {
        fmt.Println(mailman.LastErrorText())
        ssh1.DisposeSsh()
        ssh2.DisposeSsh()
        mailman.DisposeMailMan()
        email.DisposeEmail()
        return
    }

    // Close the connection with the server.  This closes the tunnel through ssh2.
    success = mailman.CloseSmtpConnection()
    if success != true {
        fmt.Println("Connection to SMTP server not closed cleanly.")
    }

    fmt.Println("Mail Sent!")

    // Close the connection with ssh2.  (This closes the the tunnel through ssh1.)
    // The connection with ssh1 is still alive, and may be used for more connections.
    ssh2.Disconnect()

    ssh1.Disconnect()

    ssh1.DisposeSsh()
    ssh2.DisposeSsh()
    mailman.DisposeMailMan()
    email.DisposeEmail()