Update

vendor/github.com/aws/smithy-go/endpoints/private/rulesfn/strings.go

@@ -0,0 +1,25 @@
+package rulesfn
+
+// Substring returns the substring of the input provided. If the start or stop
+// indexes are not valid for the input nil will be returned. If errors occur
+// they will be added to the provided [ErrorCollector].
+func SubString(input string, start, stop int, reverse bool) *string {
+	if start < 0 || stop < 1 || start >= stop || len(input) < stop {
+		return nil
+	}
+
+	for _, r := range input {
+		if r > 127 {
+			return nil
+		}
+	}
+
+	if !reverse {
+		v := input[start:stop]
+		return &v
+	}
+
+	rStart := len(input) - stop
+	rStop := len(input) - start
+	return SubString(input, rStart, rStop, false)
+}