bot_handle_message_event.go

// Run starts the run loop for the bot to listen/respond to messages
func (b *Bot) Run() {
	go b.client.ManageConnection()

	for {
		select {
		case msg := <-b.client.IncomingEvents:
			switch ev := msg.Data.(type) {
			// other types skipped for brevity
			case *slack.MessageEvent:
				userID := ev.User
				// check to see if conversation already in progress
				convo, ok := conversations[userID]

				// if not, start a new one
				if !ok {
					convo = &conversation{
						user:      userID,
						incomming: make(chan *slack.MessageEvent),
					}

					conversations[userID] = convo

					// each chat runs in its own goroutine until conversation ceases
					go b.chat(convo)
				}

				// forward incomming message to that chat's incomming channel
				convo.incomming <- ev
			}
		}
	}
}

func (b *Bot) chat(convo *conversation) {
	for convo.state = hello; convo.state != nil; {
		convo.state = convo.state(b, convo)
	}

	// conversation is over so close the incomming channel
	close(convo.incomming)
	// and delete the conversation from the map
	delete(conversations[convo.userID])
}