if (ch == 'd') {
            appendCharToStr(&token.val, ch);
            nextCh();
            if (ch == 'o') {
                appendCharToStr(&token.val, ch);
                nextCh();
                if (!isLetter(ch) || isDecDigit(ch)) {
                    return token.kind = DO;
                }
            }
        }
        if (ch == 'e') {
            appendCharToStr(&token.val, ch);
            nextCh();
            if (ch == 'l') {
                appendCharToStr(&token.val, ch);
                nextCh();
                if (ch == 's') {
                    appendCharToStr(&token.val, ch);
                    nextCh();
                    if (ch == 'e') {
                        appendCharToStr(&token.val, ch);
                        nextCh();
                        if (!isLetter(ch) || isDecDigit(ch)) {
                            return token.kind = ELSE;
                        }
                    }
                }
            }
        }
        if (ch == 'f') {
            appendCharToStr(&token.val, ch);
            nextCh();
            if (ch == 'o') {
                appendCharToStr(&token.val, ch);
                nextCh();
                if (ch == 'r') {
                    appendCharToStr(&token.val, ch);
                    nextCh();
                    if (!isLetter(ch) || isDecDigit(ch)) {
                        return token.kind = FOR;
                    }
                }
            }
        }
        if (ch == 'i') {
            appendCharToStr(&token.val, ch);
            nextCh();
            if (ch == 'f') {
                appendCharToStr(&token.val, ch);
                nextCh();
                if (!isLetter(ch) || isDecDigit(ch)) {
                    return token.kind = IF;
                }
            }
        }
        if (ch == 'w') {
            appendCharToStr(&token.val, ch);
            nextCh();
            if (ch == 'h') {
                appendCharToStr(&token.val, ch);
                nextCh();
                if (ch == 'i') {
                    appendCharToStr(&token.val, ch);
                    nextCh();
                    if (ch == 'l') {
                        appendCharToStr(&token.val, ch);
                        nextCh();
                        if (ch == 'e') {
                            appendCharToStr(&token.val, ch);
                            nextCh();
                            if (!isLetter(ch) || isDecDigit(ch)) {
                                return token.kind = WHILE;
                            }
                        }
                    }
                }
            }
        }