setter.go
func (f *FileLogger) SetMaxFileSize(size int64, unit UNIT) int64 {
	f.fileSize = size * int64(unit)
	return f.fileSize
}
func (f *FileLogger) SetMaxFileSize(size int64, unit UNIT) int64 {
	f.fileSize = size * int64(unit)
	return f.fileSize
}
// Change the sizeSplit fileLogger's single file size