code: func SampleInts(n int, k int) (res []int, err error) {
  	if k < 0 {
  		err = errors.Newf("invalid sample size k")
  		return
  	}
  
  	if n < k {
  		err = errors.Newf("sample size k larger than n")
  		return
  	}
  
  	picked := set.NewSet()
  	for picked.Len() < k {
  		i := Intn(n)
  		picked.Add(i)
  	}
  
  	res = make([]int, k)
  	e := 0
  	for i := range picked.Iter() {
  		res[e] = i.(int)
  		e++
  	}
  
  	return
  }
docs: // Samples 'k' unique ints from the range [0, n)