首先要创建两个ssh key
ssh-keygen -t rsa -C "xxx@163.com"
如果你之前已经生成过ssh key的话执行上面的指令会报错

Generating public/private rsa key pair.
//默认的输出文件就是根目录下的.ssh/id_rsa 你需要重新指定一个文件名 
//如：.ssh/id_rsa_emal1 文件名如何定义自行决定
Enter file in which to save the key (/Users/111/.ssh/id_rsa):
//这里要重新指定一个文件名，注意路径是相对路径，不然容易找不到生成的文件

下面就是正常的生成ssh key 的过程，

//设置密码，这步可以跳过
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /Users/111/.ssh/id_rsa_test.
Your public key has been saved in /Users/111/.ssh/id_rsa_test.pub.
The key fingerprint is:
SHA256:xxxxxxxxxxxxxxxxxxxxxxx
xxx@163.com
The key's randomart image is:
+---[RSA 2048]----+
|      .          |
|       +         |
|    + O .        |
| . * & = .       |
|  = X O S .      |
|   + B * *   .   |
|  . o * *   . . E|
|   . + o +..   o.|
|     .o o+=.    +|
+----[SHA256]-----+

这样新的ssh key 就生成好了