Add Docker support

[pataquets]

Add Dockerfile to enable image building. Useful for development and tests under Docker workflow.
Using the official Golang image, onbuild tag. More info at https://hub.docker.com/_/golang/
No Golang install needed on systems with Docker, both for running on production or for developing/testing.

Build:

$ docker build -t elastic-go .

Run:

$ docker run --rm -it elastic-go [options...]

FYI, there's a still quicker to test, already built image on my Docker Hub. Test it by running:

$ docker run --rm -it pataquets/elastic-go [options...]

Using --rm causes the container to be deleted after stop.

[pataquets]

@rolinh ping?

[rolinh]

Hi @pataquets,

Thanks for your contribution and sorry that it slip through the cracks.
Isn't golang:onbuild deprecated?

[SvenDowideit]

and as another example where its useful to have a docker image - our elasticsearch is in a separate docker network, and not accessible directly, so we use things like:

docker run --rm -it --net elasticsearch_esnetwork pataquets/elastic-go --baseurl http://elasticsearch:9200 index list

mmm, actually, in this case, I'd also suggest using a multi-stage build so that the resulting image is tiny - see https://github.com/SvenDowideit/elktail/blob/master/Dockerfile for an example @pataquets :)

[rolinh]

@pataquets @SvenDowideit I've added a Dockerfile in commit 0550e45. It's using a multi-stage build to optimize the image size.

[SvenDowideit]

noice!