问题：
在本地（linux系统）下载github仓库源代码时，执行git clone 命令时出现以下报错：
$ git clone git@github.com:hh-hub/prometheus.git
Cloning into 'Prometheus'...
Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
解决：
这是由于github仓库缺少公钥，把本地的公钥添加到github上即可，操作步骤如下：
1.查看本地公钥，并复制
$ cd ~/.ssh $ cat id_rsa.pub XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
2. github 添加本地公钥：Settings -> SSH and GPG keys -> new SSH key ->添加新的公钥并将本地id_rsa.pub里的内容复制到Key中，如下总共四步：
3.重新下载代码库：
$ git clone git@github.com:hh-hub/prometheus.git
Cloning into 'Prometheus'...
remote: Enumerating objects: 6, done.
remote: Counting objects: 100% (6/6), done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 6 (delta 0), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (6/6), done.
下载成功！
