Update README.md

README.md

@@ -6,6 +6,10 @@
 [![codecov](https://codecov.io/gh/shamaton/msgpack/branch/master/graph/badge.svg?token=9PD2JUK5V3)](https://codecov.io/gh/shamaton/msgpack)
 [![FOSSA Status](https://app.fossa.com/api/projects/git%2Bgithub.com%2Fshamaton%2Fmsgpack.svg?type=shield)](https://app.fossa.com/projects/git%2Bgithub.com%2Fshamaton%2Fmsgpack?ref=badge_shield)
 
+## Notice
+If your application serializes only primitive types, array, map and struct, code generation is also recommended.
+You can get the fastest performance with [msgpackgen](https://github.com/shamaton/msgpackgen).
+
 ## Features
 * Supported types : primitive / array / slice / struct / map / interface{} and time.Time
 * Renaming fields via `msgpack:"field_name"`
@@ -73,4 +77,4 @@ BenchmarkCompareDecodeGob-4                        36434             34308 ns/op
 
 ## License
 
-This library is under the MIT License.
+This library is under the MIT License.