Update Dockerfile to work with Go 1.16 Alpine image

[FnTm]

I tried to run this today, and it looks like the required go version hasn't made it to a point where the docker image label points to it. This had broken Docker image.
Got this error:

package embed is not in GOROOT (/usr/local/go/src/embed)

This is probably a super temporary fix, and may just be ok to leave this PR open in case anyone else looks at why this is not building for them.

[mkonda]

Thanks!
I am taking a separate task to both review this again when it is final and to figure out how to better test the docker image.