I am using Aws Lex for constructing chatbots. I had a scenario where I need to have welcome message initially without user input so that I can give a direction to the user in my chatbot.
If you are using your own website or an app for integrating the chatbot, then you can send some unique welcome text from that website/app when it loads for the first time i.e on load method to the amazon lex. And in amazon lex you can create a welcome intent and put exact same text as utterance.
This way, when the website/app loads, it will send text to amazon lex and lex can fire the welcome intent and reply to it.
How to get welcome messages in AWS Lex (lambda in Python)?