按照各大网站以及个人习惯我会使用下面这种方法添加Docker源：

root@ubuntu:~# sudo add-apt-repository "deb [arch=amd64] https://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu $(lsb_release -cs) stable"

然而使用上面这条命令给我带来了无尽的烦恼，甚至我都怀疑我是不是一个合格的linux工程师了，使用了这条命令提示以下错误:

Ign:1 https://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu eoan InRelease

Err:2 https://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu eoan Release
404 Not Found [IP: 218.104.71.170 443]
Hit:3 http://cn.archive.ubuntu.com/ubuntu eoan InRelease
Hit:4 http://cn.archive.ubuntu.com/ubuntu eoan-updates InRelease
Hit:5 http://cn.archive.ubuntu.com/ubuntu eoan-backports InRelease
Hit:6 http://cn.archive.ubuntu.com/ubuntu eoan-security InRelease
Reading package lists... Done 
E: The repository 'https://mirrors.ustc.edu.cn/docker-ce/linux/ubuntu eoan Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

下面是apt源文件中的内容：

deb [arch=amd64] https://download.docker.com/linux/ubuntu eoan stable
# deb-src [arch=amd64] https://download.docker.com/linux/ubuntu eoan stable
deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable 

发现是没有任何错误的，但是你会发现在使用apt更新时会出现各种各样报错，最终还是没有你想要的docker-ce安装包，还是无法安装：

root@uduntu:~# apt-get update
Get:1 http://cn.archive.ubuntu.com/ubuntu eoan InRelease [255 kB]
Get:2 http://cn.archive.ubuntu.com/ubuntu eoan-updates InRelease [88.4 kB]
Hit:3 http://cn.archive.ubuntu.com/ubuntu eoan-backports InRelease
Get:4 http://cn.archive.ubuntu.com/ubuntu eoan-security InRelease [92.9 kB]
Ign:5 https://download.docker.com/linux/ubuntu eoan InRelease                            
Err:6 https://download.docker.com/linux/ubuntu eoan Release                            
 404 Not Found [IP: 13.225.103.32 443]
Reading package lists... Done                                    
E: The repository 'https://download.docker.com/linux/ubuntu eoan Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@uduntu:~# apt search docker-ce
root@uduntu:~#

遇到这种问题我也觉得很头疼，在网上找了很多解决方法都是不行，有人都说是网络问题无法使用外网的源码库，我看到这个文章我都懵了，我还试过安装网易、阿里以及科大的源都不能更好的解决问题，其实这个很简单看一下阿里、科大和网易的他们的源码库是怎么往配置文件里面写的，然后比葫芦画瓢画一个不就完了

解决方法：

在sources.list添加下面这一条就可以：

deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable

更新apt源：

root@uduntu:~# apt-get update
Get:1 http://cn.archive.ubuntu.com/ubuntu eoan InRelease [255 kB]
Get:2 http://cn.archive.ubuntu.com/ubuntu eoan-updates InRelease [88.4 kB]
Hit:3 http://cn.archive.ubuntu.com/ubuntu eoan-backports InRelease
Get:4 http://cn.archive.ubuntu.com/ubuntu eoan-security InRelease [92.9 kB]
Get:5 https://download.docker.com/linux/ubuntu bionic InRelease [64.4 kB] 
Get:6 https://download.docker.com/linux/ubuntu bionic/stable amd64 Packages [9,594 B] Fetched 511 kB in 11s (48.3 kB/s) 
Reading package lists... Done
root@uduntu:~#