Update Dockerfile

label-schema has been deprecated in favor of OCI image spec.
if you are building in alpine 3.9, you should run in alpine 3.9 for consistency.

Dockerfile

@@ -5,7 +5,7 @@ COPY . /go/src/github.com/google/mtail
 RUN  make depclean && make install_deps && PREFIX=/go make -B install
 
 
-FROM alpine:3.7
+FROM alpine:3.9
 
 ARG version=0.0.0-local
 ARG build_date=unknown
@@ -16,16 +16,17 @@ ARG vcs_branch=unknown
 EXPOSE 3903
 ENTRYPOINT ["/usr/bin/mtail"]
 
-LABEL org.label-schema.vendor='Google' \
-    org.label-schema.name='mtail' \
-    org.label-schema.description='extract whitebox monitoring data from application logs for collection in a timeseries database' \
-    org.label-schema.usage='https://github.com/google/mtail/blob/master/docs/Programming-Guide.md' \
-    org.label-schema.url='https://github.com/google/mtail' \
-    org.label-schema.vcs-url=$vcs_url \
-    org.label-schema.vcs-branch=$vcs_branch \
-    org.label-schema.vcs-ref=$commit_hash \
-    org.label-schema.version=$version \
-    org.label-schema.schema-version='1.0' \
-    org.label-schema.build-date=$build_date
+LABEL org.opencontainers.image.ref.name="google/mtail" \
+      org.opencontainers.image.vendor="Google" \
+      org.opencontainers.image.title="mtail" \
+      org.opencontainers.image.description="extract whitebox monitoring data from application logs for collection in a timeseries database" \
+      org.opencontainers.image.authors="Jamie Wilkinson (@jaqx0r)" \
+      org.opencontainers.image.licenses="Apache-2.0" \
+      org.opencontainers.image.version=$version \
+      org.opencontainers.image.revision=$commit_hash \
+      org.opencontainers.image.source=$vcs_url \
+      org.opencontainers.image.documentation="https://github.com/google/mtail/tree/master/docs" \
+      org.opencontainers.image.created=$build_date \
+      org.opencontainers.image.url="https://github.com/google/mtail"
 
 COPY --from=builder /go/bin/mtail /usr/bin/mtail