Call Uploadcare with cross-fetch, failing on GCF

batchUploadcareUrls.js

// line 41: public & private are your Uploadcare API keys

/*

Call is nodeJS script (pass) :
  async function main() {
    const res = await pushBatchUrlsToUploadCare(['123']);
    console.log(res); // { err: { '123': 'Invalid' } }
  }

*/

/* 

Call in Graphcool resolver (fail) :

module.exports = async function(event) {
  try {
      const res = await pushBatchUrlsToUploadCare(batch);
      return { data: res };
  } catch (e) {
    ... 
  }
}
*/


const fetch = require('cross-fetch');

async function pushBatchUrlsToUploadCare(batch = ['uuid-example']) {
  try {
    if (!batch || !batch.length) {
      return { data: [] };
    }
    const batchStr = JSON.stringify(batch);

    const res = await fetch('https://api.uploadcare.com/files/storage/', {
      method: 'PUT',
      headers: {
        'Content-Type': 'application/json',
        'Authorization': `Uploadcare.Simple ${public}:${private}`
      },
      body: batchStr,
    });

    const responseData = res.json();
    return responseData.then(data => {
      if (!data.problems || !data.result) {
        return { err: 'Misformatted response and/or Batch string' };
      }
      return { data: data.result };
    })

  } catch (err) {
    console.error(err);
    return { err: 'Network request to Uploadcare failed' };
  }
}