Config-dependent Future.

ReaderTFuture.js

const Future = require('fluture')

// I can't guarantee this will work out of the box - it's quite old... but
// you should hopefully be able to see how this fits together!
const { ReaderT } = require('fantasy-readers')

// First of all, you're going to need to "lift" all your `Future` operations
// to work within ReaderT. Basically, you just need to call `ReaderT.lift` on
// any `Future` values.
const doAjaxThing_  = x => ReaderT.lift(doAjaxThing(x))
const doOtherThing_ = x => y => ReaderT.lift(doOtherThing(x)(y))

// A little app that calls `doOtherThing_` with the result of `doAjaxThing_` and
// your global config. It's "ReaderT Config (Future Error Result)"
const app =
  doAjaxThing_
  .chain(stuff =>
     ReaderT.ask // Here, we just "ask" for the config!
     .chain(config =>
        doOtherThing_(stuff)(config)))

// Future Error Result (production app)
const appOnProduction = app.run(prodConfig)

// Future Error Result (development app)
const appOnDevelopment = app.run(devConfig)

// Run as usual :)
appOnProduction
 .fork( e => console.error(e)
      , x => console.log(x)
      )