Install tensorflow runtime (#9)

This patch installs tensorflow runtime to docker image.

Dockerfile

@@ -1,23 +1,30 @@
-ARG GOVERSION=1.12
+ARG GOVERSION=1.14
 
 FROM golang:${GOVERSION}-buster
 
 # All args after each FROM command are no longer available.
 ARG COREDNSVERSION=v1.6.4
+ARG TENSORFLOWVERSION=1.15.0
 
 RUN apt-get update && apt-get -uy upgrade
 RUN apt-get -y install ca-certificates && update-ca-certificates
 
 ENV COREDNSPATH github.com/coredns/coredns
 ENV DNSTUNPATH github.com/netrack/dnstun
+ENV TENSORFLOWPATH storage.googleapis.com/tensorflow/libtensorflow
 ENV GO111MODULE on
-ENV CGO_ENABLED 0
 
 RUN curl -fsSL https://${COREDNSPATH}/archive/${COREDNSVERSION}.tar.gz -o coredns.tar.gz \
     && mkdir -p coredns \
     && tar -xzf coredns.tar.gz --strip-components=1 -C coredns \
     && rm -rf coredns.tar.gz
 
+
+RUN curl -fsSL https://${TENSORFLOWPATH}/libtensorflow-cpu-linux-x86_64-${TENSORFLOWVERSION}.tar.gz -o tensorflow.tar.gz \
+    && tar -xzf tensorflow.tar.gz -C /usr/ \
+    && rm -rf tensorflow.tar.gz \
+    && ldconfig
+
 COPY . ${GOPATH}/src/${DNSTUNPATH}
 COPY plugin.cfg coredns/plugin.cfg
 
@@ -29,8 +36,9 @@ RUN go mod edit -replace ${DNSTUNPATH}@v0.0.0=${GOPATH}/src/${DNSTUNPATH}
 RUN go generate && go build -o /bin/coredns
 
 
-FROM scratch
+FROM debian:buster-slim
 COPY --from=0 /etc/ssl/certs /etc/ssl/certs
+COPY --from=0 /usr/lib/libtensorflow* /usr/lib/
 COPY --from=0 /bin/coredns /bin/coredns
 COPY Corefile /etc/coredns/Corefile
 VOLUME /etc/coredns