How to read file asynchronously for module with then-yield

Question

I'm trying to load a secret for use with koa-jsonwebtoken.

here's the relevent bits from my koa server:

import jwt, { fromAuthorizationHeader } from 'koa-jsonwebtoken';
import {serverCredentials} from './auth'
//...
console.log('loaded serverCredentials' + JSON.stringify(serverCredentials))    
app.use(jwt({ secret: serverCredentials.shared, extractToken: fromAuthorizationHeader }));

and my auth is:

import ty from 'then-yield'
import md5 from 'md5'
import Promise from 'bluebird'
const fs = Promise.promisifyAll(require('fs'));

const serverCredentials = ty.spawn(function* () {
  let src
  try {
    console.log('trying')
    src = yield fs.readFileAsync('./serverCredentials.json','utf8')
  } catch(e) {
    console.error('Error when opening serverCredentials file: ' + e.message);
    throw e
  }
  console.log('serverCredentials: ' + src)
  return JSON.parse(src)
})

export {serverCredentials}

but my log says:

trying
loaded serverCredentials{"isFulfilled":false,"isRejected":false}

instead of the server key.

Answer 1

serverCredentials is a promise for your JSON-parsed object. You will need to wait for it:

import jwt, { fromAuthorizationHeader } from 'koa-jsonwebtoken';
import {serverCredentials as credentialsPromise} from './auth';

credentialsPromise.then(serverCredentials => {
    console.log('loaded serverCredentials' + JSON.stringify(serverCredentials))    
    app.use(jwt({secret: serverCredentials.shared, extractToken: fromAuthorizationHeader}));
});