composer 下载包时，尽管已经更换为国内镜像了https://packagist.phpcomposer.com,但是还是会报错
Content-Length mismatch, received 32372 bytes out of the expected 480707
https://packagist.phpcomposer.com could not be fully loaded, package information was loaded from the local cache and may be out of date
还是会很慢！！！！
解决办法
1、清除缓存
composer clear-cache
2、如果还是慢，更换为阿里镜像
地址：https://mirrors.aliyun.com/composer/
全局配置
composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/
取消配置
composer config -g --unset repos.packagist
当前项目配置
composer config repo.packagist composer https://mirrors.aliyun.com/composer/
取消配置
composer config --unset repos.packagist
