fix(docker) makefile, docker file multiplatform

Dockerfile

@@ -1,13 +1,16 @@
-FROM golang:1.22-alpine AS builder
+ARG TARGETOS
+ARG TARGETARCH
+
+FROM --platform=$BUILDPLATFORM golang:1.22-alpine AS builder
 WORKDIR /app
 COPY . .
-RUN go build -o prometheus-fake-remote-read ./cmd/prometheus-fake-remote-read
+RUN GOOS=$TARGETOS GOARCH=$TARGETARCH CGO_ENABLED=0 go build -o prometheus-fake-remote-read ./cmd/prometheus-fake-remote-read
 
 FROM alpine:latest
 WORKDIR /root/
 
 COPY --from=builder /app/prometheus-fake-remote-read .
 COPY --from=builder /app/configs/example.config.json .
 
-ENTRYPOINT [ "./prometheus-fake-remote-read" ]
-CMD [ "--config", "./example.config.json" ]
+ENTRYPOINT ["./prometheus-fake-remote-read"]
+CMD ["--config", "./example.config.json"]

Makefile

@@ -6,21 +6,26 @@ export
 help: ## Display this help.
 	@awk 'BEGIN {FS = ":.*##"; printf "\nUsage:\n  make \033[36m<target>\033[0m\n"} /^[a-zA-Z_0-9-]+:.*?##/ { printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2 } /^##@/ { printf "\n\033[1m%s\033[0m\n", substr($$0, 5) } ' $(MAKEFILE_LIST)
 
-##@ Helpers
+##@ Prepare
 
 .PHONY: tidy
 tidy: ## Pull up dependecies
 	go mod tidy -v
 
-.PHONY: test
-test: ## Run tests
-	go test -race -cover -v ./...
-
 .PHONY: lint
 lint: ## Run linting
 	golangci-lint run --tests=false
 	golangci-lint run --disable-all -E golint,goimports,misspell
 
+##@ Prepare
+
+.PHONY: test
+test: ## Run tests
+	go test -race -cover -v ./...
+
+.PHONY: run
+run: ## Run for current platform
+	CGO_ENABLED=0 go run ./cmd/prometheus-fake-remote-read --config configs/example.config.json
 
 ##@ Build
 
@@ -29,6 +34,9 @@ build: ## Build for current platform
 	mkdir ./bin/ || true
 	CGO_ENABLED=0 go build -o ./bin/ ./cmd/prometheus-fake-remote-read 
 
-.PHONY: run
-run: ## Run for current platform
-	CGO_ENABLED=0 go run ./cmd/prometheus-fake-remote-read --config configs/example.config.json
+.PHONY: docker-build
+docker-build: ## Test building dockerfile for multiplatforms. Using buildx
+	docker buildx create --use
+	docker buildx build --platform linux/amd64 -t prometheus-fake-remote-read:amd64 .
+	docker buildx build --platform linux/arm64 -t prometheus-fake-remote-read:arm64 .
+