Build go binary inside alpine container (prebid#595)

* Build go binary inside alpine container

* Remove unnecessary deps from Dockerfile and switch aline from edge to 3.8 version

Dockerfile

@@ -1,8 +1,19 @@
-FROM alpine
+FROM alpine:3.8 AS build
+WORKDIR /go/src/github.com/prebid/prebid-server/
+RUN apk add -U --no-cache go git dep musl-dev
+ENV GOPATH /go
+COPY ./ ./
+RUN dep ensure
+RUN go build .
+
+
+FROM alpine:3.8 AS release
 MAINTAINER Brian O'Kelley <[email protected]>
-ADD prebid-server prebid-server
+WORKDIR /usr/local/bin/
+COPY --from=build /go/src/github.com/prebid/prebid-server/prebid-server .
 COPY static static/
 COPY stored_requests/data stored_requests/data
+RUN apk add -U --no-cache ca-certificates
 EXPOSE 8000
-ENTRYPOINT ["/prebid-server"]
+ENTRYPOINT ["/usr/local/bin/prebid-server"]
 CMD ["-v", "1", "-logtostderr"]