Add Dockerfile to project (#98)

* add Dockerfile

* dockerfile: switch to multi-stage build to lighten up the final image

* dockerfile: update to latest images, and update the 2nd stage image on build

Dockerfile

@@ -0,0 +1,18 @@
+FROM golang:1.12-alpine3.10 as builder
+
+WORKDIR /go/src/vsphere-influxdb-go
+COPY . .
+RUN apk --update add --virtual build-deps git 
+RUN go get -d -v ./...
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo
+
+FROM alpine:3.10
+RUN apk update \
+ && apk upgrade \
+ && apk add ca-certificates \
+ && addgroup -S spock && adduser -S spock -G spock
+COPY --from=0 /go/src/vsphere-influxdb-go/vsphere-influxdb-go /vsphere-influxdb-go
+
+USER spock
+
+CMD ["/vsphere-influxdb-go"]