Use strings.ContainsRune instead of IndexRune

querylexer.go

diff --git a/querylexer.go b/querylexer.go
index 1532e1d..61153cb 100644
--- a/querylexer.go
+++ b/querylexer.go
@@ -105,7 +105,7 @@
 }
 
 func (l *queryLexer) accept(valid string) bool {
-	if strings.IndexRune(valid, l.next()) >= 0 {
+	if strings.ContainsRune(valid, l.next()) {
 		return true
 	}
 	l.backup()