Or AGPL. This is a fair point, and I make all of the code I write GPL. Unfortunately, there is only one containerisation project that is under the GPL and only the core of it is under the GPL (LXC is [L]GPL but LXD is not). It's quite worrying that so few Golang projects (because for some reason every containerisation project is written in Golang seemingly in anger) are under the GPL.
Make it AGPL. The GPL can be circumvented by slapping an HTTP interface on the logic, which is how Google has gotten away with keeping so much private.
Then you better don't contribute to anything that's not exactly GPL.