There is no Hangup widget as far as I know.
If your Gather widget does not get any input it will take the No input path and if that is not connected to anything, the flow will end and the call will end (hangup), you can see this by checking the Studio's logs.
But, let's say that before the end of the call if there is no input from user, you would like to let the user know and then end the call with your hangup, you could create a function under Runtime and connect No input to your own Hangup function.
The Hangup function could be something like this:
exports.handler = function(context, event, callback) {
let twiml = new Twilio.twiml.VoiceResponse();
twiml.say('No input, will hangup the call now.');
twiml.hangup();
callback(null, twiml);
};
