let obj = {
  a: 1,
  aa: 1,
  b: 2
}

let keys = Object.keys(obj);

function getKyes<T extends Record<string, unknown>>(obj: T): Array<keyof T>{
  return Object.keys(obj)
}

let r = getKyes(obj)   

// a is `('a' | 'aa' | 'b')[]` instead of `string[]`