Use go.mod, move to go 1.14, update smaller base image

[steren]

Fix #30

[steren]

oops sorry ignore for now, it doesn't run

[steren]

OK, good for review now, it runs.

[ahmetb]

If my memory serves me, we intentionally kept this to use ubuntu image base, so beginners can take a look at its source code and adapt the dockerfile for other languages in their apps.

[steren]

Mmm, on the opposite: this repo is not intended to serve as a boilerplate or hello world example.
Its single purpose is to offer the demo container. Which should contain as less as possible.

[ahmetb]

For the record, switching from alpine to Ubuntu-based image was your call: f8d7e31, 0ee75a7. I think we discussed this over a year ago as well and I was convinced Ubuntu is there so beginners can apt get new things into this sample Dockerfile with less friction. I'm indifferent otherwise. :)

[steren]

Thanks for the forensic.

My motivation was not to use Ubuntu, but to use a Google managed based image, under the assumption that it would be more secure and better maintained.

But container vulnerability scans says that Ubuntu contains a lot of known vulnerabilities. I prefer to optimize for reducing that number.

Sadly, I do not see any slim base image in gcr.io/cloud-marketplace/google, so I suggest to use alpine? Any other suggestion?