一，判断是否有已有SSH文件
ls -al ~/.ssh
如果显示如下图所示，即为没有ssh文件
No such file or directory
二，生成新的SSH KEY
在终端输入命令：
ssh-keygen -t rsa -C "github注册过的邮箱"
默认会在相应路径下（/your_home_path）生成id_rsa和id_rsa.pub两个文件，如下面代码所示
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/zhujianyi/.ssh/id_rsa):
三，输入passphrase（可以不输入）
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
结果：
Your identification has been saved in /Users/zhujianyi/.ssh/id_rsa.
Your public key has been saved in /Users/zhujianyi/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:jdasjdkajs;dja;jkdja;jskda; your_email@example.com
四，拷贝SSH KEY信息
pbcopy < ~/.ssh/id_rsa.pub
