When using apt update the following error occurs. How to correct?

Hit:1 https://repos.insights.digitalocean.com/apt/do-agent main InRelease
Ign:2 http://mirrors.digitalocean.com/ubuntu cosmic InRelease
Ign:3 http://mirrors.digitalocean.com/ubuntu cosmic-updates InRelease
Hit:4 http://ppa.launchpad.net/certbot/certbot/ubuntu cosmic InRelease
Ign:5 http://security.ubuntu.com/ubuntu cosmic-security InRelease
Ign:6 http://archive.ubuntu.com/ubuntu cosmic InRelease
Ign:7 http://mirrors.digitalocean.com/ubuntu cosmic-backports InRelease
Err:8 http://security.ubuntu.com/ubuntu cosmic-security Release
  404  Not Found [IP: 91.189.88.142 80]
Err:9 http://mirrors.digitalocean.com/ubuntu cosmic Release
  404  Not Found [IP: 104.24.116.209 80]
Err:10 http://archive.ubuntu.com/ubuntu cosmic Release
  404  Not Found [IP: 91.189.88.142 80]
Err:11 http://mirrors.digitalocean.com/ubuntu cosmic-updates Release
  404  Not Found [IP: 104.24.116.209 80]
Err:12 http://mirrors.digitalocean.com/ubuntu cosmic-backports Release
  404  Not Found [IP: 104.24.116.209 80]
Reading package lists... Done
E: The repository 'http://security.ubuntu.com/ubuntu cosmic-security Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic Release' no longer has 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 'http://archive.ubuntu.com/ubuntu cosmic Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-updates Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-backports Release' no longer has 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@asset-us:/srv/asset-us.com# sudo apt-get update
Ign:1 http://security.ubuntu.com/ubuntu cosmic-security InRelease
Err:2 http://security.ubuntu.com/ubuntu cosmic-security Release
  404  Not Found [IP: 91.189.91.38 80]
Ign:3 http://mirrors.digitalocean.com/ubuntu cosmic InRelease
Hit:4 https://repos.insights.digitalocean.com/apt/do-agent main InRelease
Ign:5 http://mirrors.digitalocean.com/ubuntu cosmic-updates InRelease
Ign:6 http://mirrors.digitalocean.com/ubuntu cosmic-backports InRelease
Err:7 http://mirrors.digitalocean.com/ubuntu cosmic Release
  404  Not Found [IP: 104.24.117.209 80]
Err:8 http://mirrors.digitalocean.com/ubuntu cosmic-updates Release
  404  Not Found [IP: 104.24.117.209 80]
Err:9 http://mirrors.digitalocean.com/ubuntu cosmic-backports Release
  404  Not Found [IP: 104.24.117.209 80]
Ign:10 http://archive.ubuntu.com/ubuntu cosmic InRelease
Hit:11 http://ppa.launchpad.net/certbot/certbot/ubuntu cosmic InRelease
Err:12 http://archive.ubuntu.com/ubuntu cosmic Release
  404  Not Found [IP: 91.189.88.152 80]
Reading package lists... Done
E: The repository 'http://security.ubuntu.com/ubuntu cosmic-security Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-updates Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-backports Release' no longer has 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 'http://archive.ubuntu.com/ubuntu cosmic Release' no longer has 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@asset-us:/srv/asset-us.com# sudo apt-get clean
root@asset-us:/srv/asset-us.com# sudo apt-get update
Hit:1 https://repos.insights.digitalocean.com/apt/do-agent main InRelease
Ign:2 http://mirrors.digitalocean.com/ubuntu cosmic InRelease
Ign:3 http://mirrors.digitalocean.com/ubuntu cosmic-updates InRelease
Ign:4 http://mirrors.digitalocean.com/ubuntu cosmic-backports InRelease
Hit:5 http://ppa.launchpad.net/certbot/certbot/ubuntu cosmic InRelease
Ign:6 http://security.ubuntu.com/ubuntu cosmic-security InRelease
Err:7 http://mirrors.digitalocean.com/ubuntu cosmic Release
  404  Not Found [IP: 104.24.117.209 80]
Ign:8 http://archive.ubuntu.com/ubuntu cosmic InRelease
Err:9 http://security.ubuntu.com/ubuntu cosmic-security Release
  404  Not Found [IP: 91.189.88.142 80]
Err:10 http://mirrors.digitalocean.com/ubuntu cosmic-updates Release
  404  Not Found [IP: 104.24.117.209 80]
Err:11 http://mirrors.digitalocean.com/ubuntu cosmic-backports Release
  404  Not Found [IP: 104.24.117.209 80]
Err:12 http://archive.ubuntu.com/ubuntu cosmic Release
  404  Not Found [IP: 91.189.88.142 80]
Reading package lists... Done
E: The repository 'http://mirrors.digitalocean.com/ubuntu cosmic Release' no longer has 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 'http://security.ubuntu.com/ubuntu cosmic-security Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-updates Release' no longer has 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 'http://mirrors.digitalocean.com/ubuntu cosmic-backports Release' no longer has 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 'http://archive.ubuntu.com/ubuntu cosmic Release' no longer has 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.