tp5 composer 切换国内镜像

我是再安装migrate的时候一直出现错误

Content-Length mismatch, received 227497 bytes out of the expected 967706
http://repo.packagist.org could not be fully loaded, package information was loaded from the local cache and may be out of date

解决办法：
再composer.json中加入

"repositories": {
        "packagist": {
            "type": "composer",
            "url": "https://packagist.phpcomposer.com"
        }
    }

其实就是把镜像变成国内的