刚才更新一个插件的时候，composer提示了一个报错：
Warning from https://repo.packagist.org: You are using an outdated version of Composer. Composer 2.0 is about to be released and the older 1.x releases will self-update directly to it once it is released. To avoid surprises update now to the latest 1.x version which will prompt you before self-updating to 2.x.
大致意思是 composer 的版本太老了，需要升级。解决办法很简单，composer 自我升级：composer selfupdate
这篇仅作为记录。
