chore: sample golang dockerfile and readme update

- variable for the foundationdb website url to the golang sample Dockerfile (similar to the python sample Dockerfile)
- added sample command to access cluster

packaging/docker/samples/golang/README.md

@@ -24,6 +24,7 @@ If you want to access the cluster from your machine, here's a `cluster file` rea
 
 ```bash
 echo "docker:docker@127.0.0.1:4500" > docker.cluster
+FDB_CLUSTER_FILE=./docker.cluster fdbcli
 ```
 
 ## Stop the golang demo

packaging/docker/samples/golang/app/Dockerfile

@@ -30,7 +30,8 @@ RUN apt update
 # dnsutils is needed to have dig installed to create cluster file
 RUN apt install -y dnsutils 
 
-RUN wget "https://www.foundationdb.org/downloads/${FDB_VERSION}/ubuntu/installers/foundationdb-clients_${FDB_VERSION}-1_amd64.deb"
+ARG FDB_WEBSITE=https://foundationdb.org
+RUN wget "${FDB_WEBSITE}/downloads/${FDB_VERSION}/ubuntu/installers/foundationdb-clients_${FDB_VERSION}-1_amd64.deb"
 RUN dpkg -i foundationdb-clients_${FDB_VERSION}-1_amd64.deb
 
 COPY --from=fdb /var/fdb/scripts/create_cluster_file.bash /