filter-headers.js

export function filterHeaders(headers, nameList) {
  return nameList
    .map(name => name.toLowerCase())
    .reduce((acc, name) => ({
      ...acc,
      [name]: headers[name]
    }, {})
    .filter(Boolean);
}

resolver.js

import { filterHeaders } from './filter-headers';

export const myResolver = {
 Query: {
   getTodo: (_, { id }, { req, dataSources }) {
     // this req has the headers we need
     const reqOptions = { 
      headers: filterHeaders(req.headers, ['x-authorization', ['x-level']) 
     };
     return dataSources.todoAPI.getTodo(id, reqOptions);
   }
 }
}

todo-datasource.js

import { RESTDataSource } from 'apollo-datasource-rest';

export class TodoAPI extends RESTDataSource {
  getTodo(id, options) {
    return this.get(`/todo/${id}`, null, options);
  }
}