Require each file in a directory, and wait for it's `_setup` function to complete

serial_promise_glob_require.js

const reqGlob = require('require-glob')

const run = async () => {
  const resolvers = await reqGlob('./resolvers/**/*.js')
  await Object.values(resolvers).reduce(
    (p, r) => p.then(() => r._setup && r._setup()),
    Promise.resolve()
  )
}

run()