Updated Dockerfile to build from scratch, decrease size from 17M to 9M

Dockerfile

@@ -7,13 +7,14 @@ RUN apk update && \
     apk --no-cache add git alpine-sdk
 
 RUN GO111MODULE=on go mod vendor
-RUN GOOS=linux go build -o binary ./
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -ldflags '-w' -o binary ./
 
-FROM alpine
+FROM scratch
 
 LABEL name="pihole-exporter"
 
 WORKDIR /root/
+
 COPY --from=builder /go/src/github.com/eko/pihole-exporter/binary pihole-exporter
 
 CMD ["./pihole-exporter"]