doc: add go playground demo

strutil/string.go

@@ -585,7 +585,7 @@ func RemoveWhiteSpace(str string, repalceAll bool) string {
 }
 
 // SubInBetween return substring between the start and end position(excluded) of source string.
-// Play: todo
+// Play: https://go.dev/play/p/EDbaRvjeNsv
 func SubInBetween(str string, start string, end string) string {
 	if _, after, ok := strings.Cut(str, start); ok {
 		if before, _, ok := strings.Cut(after, end); ok {
@@ -599,7 +599,7 @@ func SubInBetween(str string, start string, end string) string {
 // HammingDistance calculates the Hamming distance between two strings.
 // The Hamming distance is the number of positions at which the corresponding symbols are different.
 // This func returns an error if the input strings are of unequal lengths.
-// Play: todo
+// Play: https://go.dev/play/p/glNdQEA9HUi
 func HammingDistance(a, b string) (int, error) {
 	if len(a) != len(b) {
 		return -1, errors.New("a length and b length are unequal")