README.md in fluent-plugin-mysql-bulk-0.0.3 vs README.md in fluent-plugin-mysql-bulk-0.0.4

@@ -25,10 +25,10 @@
 host|database host(default: 127.0.0.1)
 database|database name(require)
 username|user(require)
 password|password(default: blank)
 column_names|bulk insert column (require)
-key_names|value key names (default : column_names)
+key_names|value key names, ${time} is placeholder Time.at(time).strftime("%Y-%m-%d %H:%M:%S") (default : column_names)
 table|bulk insert table (require)
 on_duplicate_key_update|on duplicate key update enable (true:false)
 on_duplicate_update_keys|on duplicate key update column, comma separator
 
 ## Configuration Example(bulk insert)