composer 切换镜像源

查看镜像源地址：

composer config -l

 默认是国外地址，下载会很慢，甚至加载不出来。

切换成阿里云镜像：

composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/

再次查看进项源：

composer config -l

至此，切换成功