Does that Dockerfile build a container that only has that app in and it's required dependencies? Almost all of the ones I've seen given as examples seem to have an entire copy of the OS in.
That being said, since Go binaries have no inherent dependencies, I have indeed made Docker images containing exactly one file: the Go binary. These containers are basically the same as fat binaries, with the benefits of Docker scheduling and networking at runtime.
To anyone reading this, you need some magic compiler flags in both Rust and GoLang to make sure it's a statically compiled binary (doesn't dynamically link against GNU lib-c).
But yes, this is super neat. I also like how it reads in the docker file:
FROM scratch ...
Never tried it with Rust, but I look to using Rust in the future, so I guess I better find out what the flags are for Rust.
Sidenote: It's often useful to have ca certs and timezone info. At that point it's probably not a bad idea to just use Alpine and apk add those things.
There was a recent HN article that did a step-by-step using rust+musl on Alpine. The "why" makes more sense now.