Update migrate-from-go-std.md

Author: taowen

migrate-from-go-std.md

@@ -19,7 +19,8 @@ group := ColorGroup{
 b, err := jsoniter.Marshal(group)
 ```
 
-add `import "github.com/json-iterator/go"` and repalce `json.Marshal` with `jsoniter.Marshal`. 
+Add `import "github.com/json-iterator/go"` and repalce `json.Marshal` with `jsoniter.Marshal`. Then the code should behave exactly the same, just much faster. Unlike easyjson or other json libaries, jsoniter does not rely on static code generation.
+
 `Unmarshal`, `NewEncoder`, `NewDecoder` they all works. Existing types implemented `Marshaler` or `Unmarshaler` interface will also work. Map with non-string key also work. Yes, everything just works.
 
 # 100% Compatibility