Typescript json cast any to T

typescript-json-cast-any-to-t.ts

async function typedFetch<T>(): Promise<T> {
  let res = await fetch("http://ip.jsontest.com/");
  let json = res.json();
  return json; // actually Promise<any>
}

type Ip = { ip: String };

(async function () {
  let ip = await typedFetch<Ip>();
  console.log(ip); // Ip
})();