code: func (r *importReader) readKeyword(kw string) {
  	r.peekByte(true)
  	for i := 0; i < len(kw); i++ {
  		if r.nextByte(false) != kw[i] {
  			r.syntaxError()
  			return
  		}
  	}
  	if isIdent(r.peekByte(false)) {
  		r.syntaxError()
  	}
  }
docs: // readKeyword reads the given keyword from the input.
  // If the keyword is not present, readKeyword records a syntax error.