Allow providing GeoIP license key in Dockerfile

Dockerfile

@@ -4,13 +4,19 @@ WORKDIR /go/src/github.com/mpolden/echoip
 COPY . .
 # Must build without cgo because libc is unavailable in runtime image
 ENV GO111MODULE=on CGO_ENABLED=0
-RUN make
+ARG GEOIP_LICENSE_KEY
+RUN if [ ${GEOIP_LICENSE_KEY:-} ]; then \
+    make all geoip-download ;\
+  else \
+    make all ;\
+  fi
 
 # Run
 FROM scratch
 EXPOSE 8080
 COPY --from=build \
      /go/bin/echoip \
+     /go/src/github.com/mpolden/echoip/data/ \
      /go/src/github.com/mpolden/echoip/index.html \
      /opt/echoip/
 WORKDIR /opt/echoip

Makefile

@@ -36,7 +36,7 @@ endif
 geoip-download: $(databases)
 
 docker-build:
-	$(DOCKER) build -t $(DOCKER_IMAGE) .
+	$(DOCKER) build -t $(DOCKER_IMAGE) . --build-arg GEOIP_LICENSE_KEY
 
 docker-login:
 	@echo "$(DOCKER_PASSWORD)" | $(DOCKER) login -u "$(DOCKER_USERNAME)" --password-stdin

README.md

@@ -106,6 +106,15 @@ Hub](https://hub.docker.com/r/mpolden/echoip), which can be downloaded with:
 
 `docker pull mpolden/echoip`
 
+### GeoIP support
+
+To build the Docker Image with GeoIP support follow the following steps:
+
+1. Clone the repo
+2. Get a license key. See https://blog.maxmind.com/2019/12/18/significant-changes-to-accessing-and-using-geolite2-databases/
+3. Run with replacing xxxxxxxxxxxxxxxx with the license key and USERNAME with your name: ``make docker-build GEOIP_LICENSE_KEY=xxxxxxxxxxxxxxxx DOCKER_IMAGE=USERNAME/echoip``
+4. Run the image with: ``docker run -p 8080:8080 USERNAME/echoip -f country.mmdb -c city.mmdb -a asn.mmdb
+
 ### Usage
 
 ```