Clear the existing dialog

When I enter the "reset" command, I want the conversation restart again and clear all the previous dialog, May I ask about how to do it? I had stuck for 2 days. Thank in advanced.

Here with my source code.

bot.dialog('/reset', (session) => {
    session.endDialog();

    var msg = new builder.Message(session)
        .addAttachment(welcomecard_1.welcomeCard());

    session.send(msg);
})
.triggerAction({
    matches: /^reset$/i
});

After I enter the "reset" or "/reset" the previous conversation [in red color] will remove from the dialog and this channel is using direct line.

from Clear the existing dialog