code: func (h Headers) ValidateUTF8() (string, error) {
  	for i := range h {
  		if !utf8.ValidString(h[i]) {
  			return h[i], EHDRUTF8
  		}
  	}
  	return "", nil
  }
docs: /*
  	ValidateUTF8 validates that header strings are UTF8.
  */