writer.go
func (f *FileLogger) I(format string, v ...interface{}) {
	f.Info(format, v...)
}
func (f *FileLogger) I(format string, v ...interface{}) {
	f.Info(format, v...)
}
func ( f * FileLogger ) I ( format string , v ... interface { } ) { f . Info ( format , v ... ) }
// same with Info()
same with Info ()