javascript - Exporting Node module from promise result

I'm trying to rewrite a module to return a different value than before, but now it uses an async call to get that value. (with child_process if it matters). I've wrapped it in a Promise, but that's not critical to me - it can be in the original child_process callback, but the problem is I can't chain the promise to everywhere in the app because I need this to become synchronous. Here's my module:

exec = require('child_process').exec

platformHome = process.env[if process.platform is 'win32' then 'USERPROFILE' else 'HOME']


getExecPath = new Promise (resolve, reject) ->
  path = process.env.GEM_HOME

  if path
    resolve(path)
  else
    exec 'gem environment', (err, stdout, stderr) ->
      unless err
        line = stdout.split(/\r?\n/)

                 .find((l) -> ~l.indexOf('EXECUTABLE DIRECTORY'))
        if line
          resolve line[line.indexOf(': ') + 2..]
        else
          reject undefined

GEM_HOME = undefined

getExecPath.then (path) ->
  GEM_HOME = path

.catch ->
  GEM_HOME = "#{platformHome}/.gem/ruby/2.3.0"
.then =>
  module.exports = GEM_HOME // or simply return it

Clearly, when requiring the module, this doesn't work - and if I return the promise itself, and use then after require - my next module.exports will be async, and this chain will carry on. How do I avoid this pattern?