const options = {method: 'GET'};

fetch('https://swap.ggp.gg/api/{blockchain}/permit/address', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "data": "0x000000000022D473030F116dDEE9F6B43aC78BA3"
}