code: func ReplaceInSlice(s []string, old string, new string) []string {
  	out := make([]string, 0, len(s))
  
  	for _, x := range s {
  		if x == old {
  			out = append(out, new)
  		} else {
  			out = append(out, x)
  		}
  	}
  
  	return out
  }
docs: // ReplaceInSlice replaces element old with new and returns a new slice.