reduce plural container image size

Signed-off-by: DavidSpek <[email protected]>

Author: davidspek

Dockerfile

@@ -1,8 +1,22 @@
-FROM gcr.io/pluralsh/golang:alpine AS cmd
+FROM gcr.io/pluralsh/golang:1.18.2-alpine3.15 AS builder
 
-RUN apk update && apk add --no-cache git build-base
+WORKDIR /workspace
+# Copy the Go Modules manifests
+COPY go.mod go.mod
+COPY go.sum go.sum
+# cache deps before building and copying source so that we don't need to re-download as much
+# and so that source changes don't invalidate our downloaded layer
+RUN go mod download
+
+# Copy the go source
+COPY cmd/ cmd/
+COPY pkg/ pkg/
 
-WORKDIR $GOPATH/src/plural/
-COPY . .
-RUN go build -o /go/bin/plural -ldflags '-s -w' ./cmd/plural/
-RUN /go/bin/plural --help
+# Build
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o plural -ldflags '-s -w' ./cmd/plural/
+
+FROM gcr.io/pluralsh/golang:1.18.2-alpine3.15
+RUN apk update && apk add --no-cache git build-base
+WORKDIR /
+COPY --from=builder /workspace/plural /go/bin/
+RUN /go/bin/plural --help