Display available versions of a package in Debian/Ubuntu

$ apt-cache madison docker.io
 docker.io | 19.03.12+dfsg1-3 | http://deb.debian.org/debian bullseye/main amd64 Packages
 docker.io | 19.03.12+dfsg1-3 | http://ftp.de.debian.org/debian bullseye/main amd64 Packages
 docker.io | 19.03.4+dfsg2-2 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.5+dfsg1-1 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.6+dfsg1-2 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.6+dfsg1-4 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.7+dfsg1-1 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.11+dfsg1-1 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.12+dfsg1-1 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.12+dfsg1-3 | http://deb.debian.org/debian bullseye/main Sources
 docker.io | 19.03.4+dfsg2-2 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.5+dfsg1-1 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.6+dfsg1-2 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.6+dfsg1-4 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.7+dfsg1-1 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.11+dfsg1-1 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.12+dfsg1-1 | http://ftp.de.debian.org/debian bullseye/main Sources
 docker.io | 19.03.12+dfsg1-3 | http://ftp.de.debian.org/debian bullseye/main Sources