code: func dedupe(s []string) []string {
  	var out []string
  	m := make(map[string]bool)
  
  	for _, char := range s {
  		if _, ok := m[char]; !ok {
  			m[char] = true
  			out = append(out, char)
  		}
  	}
  
  	return out
  }
docs: // dudupe removes duplicate characters from s.