chore: upgrade coredns version (#550)

vendor/github.com/expr-lang/expr/parser/utils/utils.go

@@ -0,0 +1,34 @@
+package utils
+
+import (
+	"unicode"
+	"unicode/utf8"
+)
+
+func IsValidIdentifier(str string) bool {
+	if len(str) == 0 {
+		return false
+	}
+	h, w := utf8.DecodeRuneInString(str)
+	if !IsAlphabetic(h) {
+		return false
+	}
+	for _, r := range str[w:] {
+		if !IsAlphaNumeric(r) {
+			return false
+		}
+	}
+	return true
+}
+
+func IsSpace(r rune) bool {
+	return unicode.IsSpace(r)
+}
+
+func IsAlphaNumeric(r rune) bool {
+	return IsAlphabetic(r) || unicode.IsDigit(r)
+}
+
+func IsAlphabetic(r rune) bool {
+	return r == '_' || r == '$' || unicode.IsLetter(r)
+}