code: func (s *scanner) SkipSpaces() (rune, bool) {
  	r, ok := s.Next()
  	for unicode.IsSpace(r) && ok {
  		r, ok = s.Next()
  	}
  	return r, ok
  }
docs: // SkipSpaces returns the next non-whitespace rune.
  // It returns 0, false if the end of the text has been reached.