How can i get the certificate files from greenlock-express for use with Nginx?

Question

I am using the greenlock-express libary for node.js

My init config looks like this:

    const greenlock = require("greenlock-express")
        .init({
            packageRoot: global.__projectFolder,
            configDir: "./greenlock.d",
            maintainerEmail: "x@example.com",
            cluster: false
        })
        .serve(app)

I use Nginx as proxy server and want to integrate the SSL certificates created with Greenlock. Where can I find them?