file：<string> | <Buffer> | <URL> 要写入的文件路径（模式由 append 选项控制）。
file
¥file: <string> | <Buffer> | <URL> A path to a file to be written to (mode controlled by the append option).
重新打开文件，用于日志轮换。
¥Reopen the file in place, useful for log rotation.