. However made some change . pasting the content below
FROM golang:1.13-alpine
#RUN apk update && apk add bash
RUN apk add --no-cache --update alpine-sdk
COPY . /go/src/
github.com/dexidp/dexRUN cd /go/src/
github.com/dexidp/dex && make release-binary
FROM alpine:3.10
# Dex connectors, such as GitHub and Google logins require root certificates.
# Proper installations should manage those certificates, but it's a bad user
# experience when this doesn't work out of the box.
#
# OpenSSL is required so wget can query HTTPS endpoints for health checking.
RUN apk add --update ca-certificates openssl
USER 1001:1001
COPY --from=0 /go/bin/dex /usr/local/bin/dex
# Import frontend assets and set the correct CWD directory so the assets
# are in the default path.
COPY web /web
#The folder /go is missing in the container. Not sure at some point it's getting deleted
#Hence copying again
COPY . /
WORKDIR /
ENTRYPOINT ["dex"]
CMD ["serve","examples/config-dev.yaml"]