code: func lexComment(l *Lexer) lexFunc {
  	if str := l.findRegexp(l.closeComment); str != "" {
  		l.pos += len(str)
  		l.emit(TokenComment)
  
  		return lexContent
  	}
  
  	if r := l.next(); r == eof {
  		return l.errorf("Unclosed comment")
  	}
  
  	return lexComment
  }
docs: // lexComment scans {{!-- or {{!