update dockerfile to add user

Signed-off-by: Carlos Panato <ctadeu@gmail.com>

sample-functions/ApiKeyProtected-Secrets/Dockerfile

-FROM golang:1.9.7-alpine as builder
+FROM golang:1.10.4-alpine3.8 as builder
 
-MAINTAINER alex@openfaas.com
-ENTRYPOINT []
+# Allows you to add additional packages via build-arg
+ARG ADDITIONAL_PACKAGE
+ARG CGO_ENABLED=0
 
-RUN apk --no-cache add make curl \
-    && curl -sL https://github.com/openfaas/faas/releases/download/0.13.0/fwatchdog > /usr/bin/fwatchdog \
-    && chmod +x /usr/bin/fwatchdog
+RUN apk --no-cache add curl ${ADDITIONAL_PACKAGE} \
+  && echo "Pulling watchdog binary from Github." \
+  && curl -sSL https://github.com/openfaas/faas/releases/download/0.13.0/fwatchdog > /usr/bin/fwatchdog \
+  && chmod +x /usr/bin/fwatchdog \
+  && apk del curl --no-cache
 
-WORKDIR /go/src/github.com/openfaas/faas/sample-functions/ApiKeyProtected
+WORKDIR /go/src/handler
+COPY . .
 
-COPY handler.go .
-# COPY vendor vendor
+# Run a gofmt and exclude all vendored code.
+RUN test -z "$(gofmt -l $(find . -type f -name '*.go' -not -path "./vendor/*" -not -path "./function/vendor/*"))" || { echo "Run \"gofmt -s -w\" on your Golang code"; exit 1; }
 
-RUN go install
+RUN CGO_ENABLED=${CGO_ENABLED} GOOS=linux \
+  go build --ldflags "-s -w" -a -installsuffix cgo -o handler . && \
+  go test $(go list ./... | grep -v /vendor/) -cover
 
 FROM alpine:3.8
+RUN apk --no-cache add ca-certificates
 
-# Needed to reach the hub
-RUN apk --no-cache add ca-certificates 
+# Add non root user
+RUN addgroup -S app && adduser -S -g app app
+RUN mkdir -p /home/app
+
+WORKDIR /home/app
+
+COPY --from=builder /usr/bin/fwatchdog         .
+
+COPY --from=builder /go/src/handler/function/  .
+COPY --from=builder /go/src/handler/handler    .
 
-COPY --from=builder /usr/bin/fwatchdog  /usr/bin/fwatchdog
-COPY --from=builder /go/bin/ApiKeyProtected  /usr/bin/ApiKeyProtected
 ENV fprocess "/usr/bin/ApiKeyProtected"
 
-CMD ["/usr/bin/fwatchdog"]
+RUN chown -R app /home/app
+
+USER app
+
+ENV fprocess="./handler"
+EXPOSE 8080
+
+HEALTHCHECK --interval=3s CMD [ -e /tmp/.lock ] || exit 1
+
+CMD ["./fwatchdog"]