add the Dockerfile

Dockerfile

@@ -0,0 +1,21 @@
+# build stage
+FROM golang:alpine AS build-env
+ENV WORKDIR /go/src/github.com/castawaylabs/cachet-monitor
+RUN mkdir -p ${WORKDIR}
+ADD . ${WORKDIR}
+WORKDIR ${WORKDIR}
+RUN apk add --no-cache ca-certificates git
+RUN go get -v github.com/Sirupsen/logrus \
+      github.com/docopt/docopt-go \
+      github.com/mitchellh/mapstructure \
+      gopkg.in/yaml.v2 \
+      github.com/miekg/dns
+RUN cd cli && go build -o /app/cachet-monitor
+
+# final stage
+FROM alpine
+RUN apk add --no-cache ca-certificates
+COPY --from=build-env /app/cachet-monitor /app/
+WORKDIR /app
+RUN chmod a+x cachet-monitor
+ENTRYPOINT ["/app/cachet-monitor"]