Launch.json file that works on VSCode 1.30.1, node 8, run via play button.

launch.json

{
    "version": "0.2.0",
    "configurations": [  
        {
            "type": "node",
            "request": "launch",
            "name": "Launch in WSL",
            "useWSL": true,
            "program": "${workspaceFolder}/app.js"
        }
    ]
}