add single quote string

core/lexer.go

@@ -303,6 +303,22 @@ func (l *Lexer) NextToken() (Token, error) {
 
 		return l.makeToken(TokenString), nil
 
+	case '\'':
+		// include ending quote
+		for !l.accept('\'') {
+			if l.match('\n') {
+				return l.makeToken(TokenError), errors.New("string did not end in current line")
+			}
+
+			if l.isAtEnd() {
+				return l.makeToken(TokenError), errors.New("string did not before end of source")
+			}
+
+			l.advance()
+		}
+
+		return l.makeToken(TokenString), nil
+
 	default:
 		if unicode.IsLetter(c) || c == '_' {
 			// assemble variable