func (x *hclLex) Lex(yylval *hclSymType) int {
	for {
		c := x.next()
		if c == lexEOF {
			return lexEOF
		}
		if unicode.IsSpace(c) {
			x.lastNumber = false
			continue
		}
		switch c {
		case '#':
			fallthrough
		case '/':
			if !x.consumeComment(c) {
				return lexEOF
			}
			continue
		}
		if c >= '0' && c <= '9' {
			x.lastNumber = true
			x.backup()
			return x.lexNumber(yylval)
		}
		if x.lastNumber {
			switch c {
			case 'e':
				fallthrough
			case 'E':
				switch x.next() {
				case '+':
					return EPLUS
				case '-':
					return EMINUS
				default:
					x.backup()
					return EPLUS
				}
			}
		}
		x.lastNumber = false
		switch c {
		case '.':
			return PERIOD
		case '-':
			return MINUS
		case ',':
			return x.lexComma()
		case '=':
			return EQUAL
		case '[':
			return LEFTBRACKET
		case ']':
			return RIGHTBRACKET
		case '{':
			return LEFTBRACE
		case '}':
			return RIGHTBRACE
		case '"':
			return x.lexString(yylval)
		case '<':
			return x.lexHeredoc(yylval)
		default:
			x.backup()
			return x.lexId(yylval)
		}
	}
}
The parser calls this method to get each new token.
package hcl
import (
	"bytes"
	"fmt"
	"strconv"
	"unicode"
	"unicode/utf8"
)
const lexEOF = 0
type hclLex struct {
	Input string
	lastNumber        bool
	pos               int
	width             int
	col, line         int
	lastCol, lastLine int
	err               error
}