Multi-stage docker build

Author: BehnH

.dockerignore

@@ -0,0 +1,12 @@
+.git/
+.github/
+images/
+testdata/
+
+.gitignore
+.ldignore
+action.yml
+CODEOWNERS
+
+*.md
+Makefile

Dockerfile

@@ -1,18 +1,24 @@
+FROM --platform=$BUILDPLATFORM golang:alpine AS builder
+ARG TARGETOS
+ARG TARGETARCH
+
+ENV GO111MODULE=on
+WORKDIR /app
+
+COPY . .
+
+RUN go mod download
+RUN GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build .
+
 FROM golang:alpine
+
 LABEL com.github.actions.name="LaunchDarkly Find Flags"
 LABEL com.github.actions.description="Flags"
 LABEL homepage="https://www.launchdarkly.com"
 
 RUN apk update
 RUN apk add --no-cache git
 
-RUN mkdir /app
-WORKDIR /app
-COPY . .
-ENV GO111MODULE=on
-RUN go mod download
-RUN go build .
-
-
+COPY --from=builder /app/find-code-references-in-pull-request /usr/bin
 
-ENTRYPOINT ["/app/find-code-references-in-pull-request"]
+ENTRYPOINT ["find-code-references-in-pull-request"]