add Dockerfile & CI

based off b3vis/apcupsd_exporter

.gitlab-ci.yml

+stages:
+  - build
+
+image: docker:latest
+
+services:
+  - name: docker:dind
+    command: [ "--insecure-registry=registry.cslab" ]
+
+before_script:
+  - docker info
+
+build:
+  stage: build
+  script:
+    - docker build
+        --tag registry.cslab/prometheus/apcupsd-exporter:latest
+        .
+    - docker push registry.cslab/prometheus/apcupsd-exporter:latest
+  tags:
+    - dind

Dockerfile

+FROM golang:alpine AS build
+RUN apk add --no-cache git \
+	&& go get -u github.com/mdlayher/apcupsd_exporter \
+	&& go get -t -v ./..
+
+FROM alpine:latest
+COPY --from=build /go/bin/apcupsd_exporter /usr/local/bin/apcupsd_exporter
+EXPOSE 9162
+CMD /usr/local/bin/apcupsd_exporter -apcupsd.addr $APCUPSDADDR