adding .goreleaser.yml

[poblahblahblah]

Proposed changes

This adds support for goreleaser, which is to help build binaries for various platforms and architectures. This is so people don't have to build the binaries themselves. Other exporters are currently using this and it is super handy for the community.

Usage is:

commit, push and tag new version (e.g. v1.1.2)
run go get github.com/goreleaser/goreleaser (only the first time)
export GITHUB_TOKEN=YOUR_TOKEN (generated with repo scope)
goreleaser --rm-dist [--release-notes FILE] [--skip-publish if you want to test it] - this will build all binaries, archive them to tar.gz and create new release on github

for more info see https://goreleaser.com/

This PR was inspired by discordianfish/nginx_exporter#35

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING guide
• I have proven my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have ensured the README is up to date
• I have rebased my branch onto master
• I will ensure my PR is targeting the master branch and pulling from my branch on my own fork

[pleshakov]

@poblahblahblah thanks for the PR.

While this tool seems handy, I don't see a need for it in our release process. Currently, we haven't had any requests for releasing binaries with the release, and the Docker image on DockerHub is our primary release artifact. If we need to release binaries in the future, we will consider using this tool.

Thanks for the suggestion!

[poblahblahblah]

@pleshakov I think you can consider this a request for pre-built binaries with the releases.

[pleshakov]

@poblahblahblah
great!
for your case, what is the platform that you use?
the list of platforms that is supported by our official packages is here http://nginx.org/en/linux_packages.html

[poblahblahblah]

@pleshakov We would like binaries for RHEL/CentOS 6.x and 7.x, Ubuntu 16.04, and 18.04. All x86_64.

[pleshakov]

@poblahblahblah
for every new release, we'll be releasing binaries for amd64 and i386 for Linux.
Additionally, we updated the latest 0.1.0 release --https://github.com/nginxinc/nginx-prometheus-exporter/releases/tag/v0.1.0 with the binaries.

Binaries can be built using the Makefile