How to yield in a resolver? about koa-graphql HOT 3 CLOSED

new GraphQLObjectType({
  name: 'MyType',
  fields: {
    myField: {
      type: GraphQLString,
      resolve: function (parentValue, args, session) {
        return fetch('/some/api')
          .then(res => res.json())
          .then(json => json.myKey);
      }
    }
  }
});

const co = require('co');

new GraphQLObjectType({
  name: 'MyType',
  fields: {
    myField: {
      type: GraphQLString,
      resolve: co.wrap(function *(parentValue, args, session) {
        const res = yield fetch('/some/api');
        const json = yield res.json();
        return json.myKey;
      })
    }
  }
});