add support for docker swarm secrets paperkey

Dockerfile

@@ -5,9 +5,11 @@ COPY . .
 RUN go get -d -v
 RUN go build -o app .
 
-FROM keybaseio/client:latest
+FROM keybaseio/client:stable-slim
 
 WORKDIR /home/keybase
 COPY --from=builder /go/src/app/app .
+COPY --from=builder /go/src/app/provision.sh .
 ENV KEYBASE_SERVICE=1
-CMD ["./app"]
+RUN chmod +x provision.sh
+CMD ["./provision.sh"]

provision.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+keybase --no-auto-fork \
+    oneshot \
+    -u $KEYBASE_USERNAME \
+    --paperkey "$(cat /run/secrets/$KEYBASE_USERNAME-paperkey)"
+./app