doc: add go playground demo

compare/compare.go

@@ -66,6 +66,7 @@ func GreaterOrEqual(left, right any) bool {
 }
 
 // InDelta checks if two values are equal or not within a delta.
+// Play: https://go.dev/play/p/TuDdcNtMkjo
 func InDelta[T constraints.Integer | constraints.Float](left, right T, delta float64) bool {
 	return float64(mathutil.Abs(left-right)) <= delta
 }

cryptor/basic.go

@@ -105,7 +105,7 @@ func HmacMd5(str, key string) string {
 }
 
 // HmacMd5WithBase64 return the hmac hash of string use md5 with base64.
-// todo
+// https://go.dev/play/p/UY0ng2AefFC
 func HmacMd5WithBase64(data, key string) string {
 	h := hmac.New(md5.New, []byte(key))
 	h.Write([]byte(data))