Build binary within Docker image

This is good for reproducible builds

Makefile

@@ -9,7 +9,8 @@ BINARY_NAME := gostatsd
 IMAGE_NAME := atlassianlabs/$(BINARY_NAME)
 ARCH ?= darwin
 METALINTER_CONCURRENCY ?= 4
-GOVERSION = 1.6.2
+GOVERSION := 1.6.2
+GP := /gopath
 
 setup: setup-ci
 	go get -v -u github.com/githubnemo/CompileDaemon
@@ -85,19 +86,24 @@ git-hook:
 	cp dev/push-hook.sh .git/hooks/pre-push
 
 # Compile a static binary. Cannot be used with -race
-cross:
-	CGO_ENABLED=0 GOOS=linux go build -o build/bin/linux/$(BINARY_NAME) $(GOBUILD_VERSION_ARGS) -a -installsuffix cgo github.com/atlassian/gostatsd
-
-docker: cross
+docker:
+	docker run \
+		--rm \
+		-v "$(GOPATH)":"$(GP)" \
+		-w "$(GP)/src/github.com/atlassian/gostatsd" \
+		-e GOPATH="$(GP)" \
+		-e CGO_ENABLED=0 \
+		golang:$(GOVERSION) \
+		go build -o build/bin/linux/$(BINARY_NAME) $(GOBUILD_VERSION_ARGS) -a -installsuffix cgo github.com/atlassian/gostatsd
 	docker build --pull -t $(IMAGE_NAME):$(GIT_HASH) build
 
-# Compile a binary with -race.
+# Compile a binary with -race. Needs to be run on a glibc-based system.
 docker-race:
 	docker run \
 		--rm \
-		-v "$(GOPATH)":/opt/gopath \
-		-w /opt/gopath/src/github.com/atlassian/gostatsd \
-		-e GOPATH=/opt/gopath \
+		-v "$(GOPATH)":"$(GP)" \
+		-w "$(GP)/src/github.com/atlassian/gostatsd" \
+		-e GOPATH="$(GP)" \
 		golang:$(GOVERSION) \
 		go build -race -o build/bin/linux/$(BINARY_NAME) $(GOBUILD_VERSION_ARGS) -a -installsuffix cgo github.com/atlassian/gostatsd
 	docker build --pull -t $(IMAGE_NAME):$(GIT_HASH)-race -f build/Dockerfile-glibc build
@@ -111,6 +117,9 @@ release-normal: release-hash
 	docker tag $(IMAGE_NAME):$(GIT_HASH) $(IMAGE_NAME):$(REPO_VERSION)
 	docker push $(IMAGE_NAME):$(REPO_VERSION)
 
+release-hash-race: check test docker-race
+	docker push $(IMAGE_NAME):$(GIT_HASH)-race
+
 release-race: docker-race
 	docker tag $(IMAGE_NAME):$(GIT_HASH)-race $(IMAGE_NAME):$(REPO_VERSION)-race
 	docker push $(IMAGE_NAME):$(REPO_VERSION)-race