GCP Dataflow Go Flex Template - COPY wordcount: failed to compute cache key: "/wordcount" not found: not found

Question

I've been building python flex templates and would like to test out one in go. Following this tutorial I ran into an error running docker build .

My guess is that there is something simple I'm missing to do with setting up a go package

image

FROM gcr.io/dataflow-templates-base/go-template-launcher-base

ARG WORKDIR=/dataflow/template
RUN mkdir -p ${WORKDIR}

COPY wordcount ${WORKDIR}/wordcount

ENV FLEX_TEMPLATE_GO_BINARY="${WORKDIR}/wordcount"

ENTRYPOINT ["/opt/google/dataflow/go_template_launcher"]

error

 => ERROR [3/3] COPY wordcount /dataflow/template/wordcount                                                            0.0s
------
 > [3/3] COPY wordcount /dataflow/template/wordcount:
------
failed to compute cache key: "/wordcount" not found: not found

tree

.
├── Dockerfile
├── README.md
├── metadata.json
├── wordcount.go
└── wordcount_test.go