ci: move build inside Dockerfile

Dockerfile

@@ -1,3 +1,25 @@
+FROM golang:1.20.0 as deps
+WORKDIR /build
+ADD go.* /build
+RUN go mod download
+
+FROM deps as build
+ENV CGO_ENABLED=0
+ADD . /build
+RUN if [ $(go mod tidy -v 2>&1 | grep -c unused) != 0 ]; then echo "Unused modules, please run 'go mod tidy'"; exit 1; fi
+RUN go fmt ./...
+RUN go vet ./...
+RUN CGO_ENABLED=1 go test -mod=readonly -race -coverprofile=coverage.txt.tmp -covermode=atomic -coverpkg=$(go list ./... | tr '\n' , | sed 's/,$//') ./...
+RUN ["/bin/bash", "-c", "cat coverage.txt.tmp | grep -v -f <(find . -type f | xargs grep -l 'Code generated') > coverage.txt"]
+RUN go tool cover -html=coverage.txt -o coverage.html
+RUN go tool cover -func=coverage.txt
+RUN rm coverage.txt.tmp
+RUN GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -mod=readonly -o release/default-request-adder -ldflags '-w -s'
+
+FROM scratch as export
+COPY --from=build /build/coverage.txt /
+
 FROM scratch
-COPY release/default-request-adder /
+COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=build /build/release/default-request-adder /
 CMD ["/default-request-adder"]