I think I will stick with a Docker. DEB packages are very complicated and this tool does not really handle dependency conflits and so on that well. Plus it does not work with RPM and other packages systems.
Not really, it's just a tar file with some metadata. Using fpm¹, making packages from a directory is extremely simple. I've been building internal packages from our different components, and the build script only has three or four lines. And besides, even Dockerfiles often use apt/yum.
This is a problem for Go programs, due to multiple unversioned (usually) dependencies on other Go libraries.
I'm not going to be building .debs for installation inside Docker containers (turtles all the way down) but I would still consider something like aptly for storing and managing any obscure dependencies that my applications might require, and for maintaining a mirror on the local network to speed up image builds.