Nit -- you want:

    async function main () {
      try {
        const jsons = await Promise.all([
          fetch('https://api.github.com/orgs/facebook'),
          fetch('https://api.github.com/orgs/facebook')
        ].map(promise => promise.then(res => res.json())));
      } catch (err) {
        console.log(err)
      }
    }

As written you get "Promise.all(...).map is not a function"