Using Visual Studio Code on MacOS "Error: No default engine was specified and no extension was provided."
Seems that pug view rendering engine NOT INSTALLED locally as a depency, even though I installed Express globally with npm install -g express-generator
Fix

run a terminal window, or press CTRL-`(backtick) from inside of Visual Studio Code
cd into your project directory/folder - or already there if launched the terminal from VSCode (previous step)... from there run these commands:

install pug as a local dependency with npm install pug
for EXTRA good measure, re-install express locally with: npm install express
ensure all dependencies are installed and updated using: npm install
relaunch your application with:   npm start
test/view your application at: http://localhost:3000