Inside the RequestHandler, override the ResponseBuilder to be able to send multiple "speak" requests to concat. This makes it easier to pass between different handlers/functions, each can add a preamble if required (e.g. "Game over..." + "Starting a new game").

RequestHandler.js

const RequestHandler = {
    
    process(handlerInput) {
        //log our request
        console.log("REQUEST ENVELOPE = " + JSON.stringify(handlerInput.requestEnvelope));
        
        //required function taken from Alexa SDK
        function trimOutputSpeech(speechOutput) {
            if (!speechOutput) {
                return '';
            }
            var speech = speechOutput.trim();
            var length = speech.length;
            if (speech.startsWith('<speak>') && speech.endsWith('</speak>')) {
                return speech.substring(7, length - 8).trim();
            }
            return speech;
        }
        //required function taken from Alexa SDK
        function isVideoAppLaunchDirectivePresent() {
            let responseBuilder = handlerInput.responseBuilder;
            let response = responseBuilder.getResponse();
            if (!response.directives) {
                return false;
            }
            for (var _i = 0, _a = response.directives; _i < _a.length; _i++) {
                var directive = _a[_i];
                if (directive.type === 'VideoApp.Launch') {
                    return true;
                }
            }
            return false;
        }

        //add support for multiple "speak" commands to make it easier to pass requests between handlers.
        handlerInput.responseBuilder.speak = function(speechOutput, playBehavior){
            let responseBuilder = handlerInput.responseBuilder;
            let response = responseBuilder.getResponse();
            responseBuilder.outputSpeakArray = responseBuilder.outputSpeakArray || [];
            responseBuilder.outputSpeakArray.push(trimOutputSpeech(speechOutput+""));

            response.outputSpeech = {
                type: 'SSML',
                ssml: '<speak>'
                    + responseBuilder.outputSpeakArray.join(" ")
                    + '</speak>',
                playBehavior: playBehavior,
            };
            if (!playBehavior) {
                delete response.outputSpeech.playBehavior;
            }
            return this;
        };

        //add support for multiple "reprompt" commands to make it easier to pass requests between handlers.
        handlerInput.responseBuilder.reprompt = function(repromptSpeechOutput, playBehavior){
            let responseBuilder = handlerInput.responseBuilder;
            let response = responseBuilder.getResponse();
            responseBuilder.outputRepromptArray = responseBuilder.outputRepromptArray || [];
            responseBuilder.outputRepromptArray.push(trimOutputSpeech(repromptSpeechOutput+""));

            response.reprompt = {
                outputSpeech: {
                    type: 'SSML',
                    ssml: '<speak>'
                        + responseBuilder.outputRepromptArray.join(" ")
                        + '</speak>',
                    playBehavior: playBehavior,
                },
            };
            if (!playBehavior) {
                delete response.reprompt.outputSpeech.playBehavior;
            }
            if (!isVideoAppLaunchDirectivePresent()) {
                response.shouldEndSession = false;
            }
            return this;
        };
    }
};