title: Unable to add docker repository to Ubuntu 18.10 - cosmic
body: <p>Trying to install Docker in Ubuntu 18.10(cosmic). I am unable to add docker repository if I execute below comand:
  sudo add-apt-repository "deb [arch=amd64] <a href="https://download.docker.com/linux/ubuntu" rel="nofollow noreferrer">https://download.docker.com/linux/ubuntu</a> $(lsb_release -cs) stable"</p>
  
  <p>Below is error detail:</p>
  
  <pre><code> Ign:1 https://download.docker.com/linux/ubuntu cosmic InRelease
      Hit:2 http://archive.ubuntu.com/ubuntu cosmic InRelease
      Ign:3 https://download.docker.com/linux/ubuntu Bionic InRelease         
      Hit:4 http://archive.ubuntu.com/ubuntu cosmic-updates InRelease         
      Hit:5 http://archive.ubuntu.com/ubuntu cosmic-backports InRelease        
      Err:6 https://download.docker.com/linux/ubuntu cosmic Release            
        404  Not Found [IP: 2600:9000:2098:7e00:3:db06:4200:93a1 443]
      Hit:7 http://archive.ubuntu.com/ubuntu cosmic-security InRelease         
      Err:8 https://download.docker.com/linux/ubuntu Bionic Release
        404  Not Found [IP: 2600:9000:2098:7e00:3:db06:4200:93a1 443]
      Reading package lists... Done
      E: T**he repository 'https://download.docker.com/linux/ubuntu cosmic 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.
      E: **The repository 'https://download.docker.com/linux/ubuntu Bionic 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.
  </code></pre>