update Dockerfile to use wolfi for building multi-arch images

Signed-off-by: Taylor Silva <dev@taydev.net>

Author: taylorsilva

Dockerfile

@@ -1,20 +1,26 @@
-ARG base_image=concourse/resource-types-base-image-static:latest
+ARG base_image=cgr.dev/chainguard/wolfi-base
 ARG builder_image=concourse/golang-builder
 
-FROM ${builder_image} AS builder
-COPY . $GOPATH/src/github.com/concourse/github-release-resource
+ARG BUILDPLATFORM
+FROM --platform=${BUILDPLATFORM} ${builder_image} AS builder
+
+ARG TARGETOS
+ARG TARGETARCH
+ENV GOOS=$TARGETOS
+ENV GOARCH=$TARGETARCH
+
+COPY . /src
+WORKDIR /src
 ENV CGO_ENABLED=0
-WORKDIR $GOPATH/src/github.com/concourse/github-release-resource
-RUN go mod vendor
-RUN go build -o /assets/out github.com/concourse/github-release-resource/cmd/out
-RUN go build -o /assets/in github.com/concourse/github-release-resource/cmd/in
-RUN go build -o /assets/check github.com/concourse/github-release-resource/cmd/check
+RUN go mod download
+RUN go build -o /assets/out ./cmd/out
+RUN go build -o /assets/in ./cmd/in
+RUN go build -o /assets/check ./cmd/check
 RUN set -e; for pkg in $(go list ./...); do \
 		go test -o "/tests/$(basename $pkg).test" -c $pkg; \
 	done
 
 FROM ${base_image} AS resource
-USER root
 COPY --from=builder /assets /opt/resource
 
 FROM resource AS tests

README.md

@@ -210,7 +210,7 @@ will stop the build.
 Run the tests with the following command:
 
 ```sh
-docker build -t github-release-resource --target tests --build-arg base_image=concourse/resource-types-base-image-static:latest .
+docker build -t github-release-resource --target tests .
 ```
 
 ### Contributing