After you run amplify add function, navigate to src directory using terminal, and then run the following command:
rm index.js package.json event.json && \
git clone https://github.com/hackmajoris/amplify-ts-lambda-skeleton.git && \
cp -r amplify-ts-lambda-skeleton/{.,}* ./ && rm -rf amplify-ts-lambda-skeleton && \
rm -rf .git README.md && \
npm install && npm run-script tsc
After the success execution, open package.json and change the name of the function to the name of your function at the amplify:<LAMBDA_NAME>action (make sure that you change also the path).
You can test then the function by running amplify mock function -> LAMBDA_NAME.