doc: update readme document for migration

README.md

@@ -562,6 +562,14 @@ Then run the following command to compile the migration files into go files:
 make migrations
 ```
 
+or
+
+```shell
+	rockhopper compile --config rockhopper_mysql.yaml --output pkg/migrations/mysql
+	rockhopper compile --config rockhopper_sqlite.yaml --output pkg/migrations/sqlite3
+	git add -v pkg/migrations && git commit -m "compile and update migration package" pkg/migrations || true
+```
+
 
 If you want to override the DSN and the Driver defined in the YAML config file, you can add some env vars in your dotenv file like this:
 

migrations/mysql/20211211103657_update_fee_currency_length.sql

@@ -0,0 +1,9 @@
+-- +up
+-- +begin
+ALTER TABLE trades CHANGE fee_currency fee_currency varchar(10) NOT NULL;
+-- +end
+
+-- +down
+-- +begin
+ALTER TABLE trades CHANGE fee_currency fee_currency varchar(4) NOT NULL;
+-- +end

migrations/sqlite3/20211211103657_update_fee_currency_length.sql

@@ -0,0 +1,8 @@
+-- +up
+-- +begin
+-- +end
+
+-- +down
+
+-- +begin
+-- +end