Dockerfile: use GO_VERSION build-arg for overriding Go version

This allows overriding the version of Go without making modifications in the
source code, which can be useful to test against multiple versions.

For example:

    make GO_VERSION=1.13beta1 -f docker.Makefile binary

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docker.Makefile

@@ -27,32 +27,32 @@ ENVVARS = -e VERSION=$(VERSION) -e GITCOMMIT -e PLATFORM -e TESTFLAGS -e TESTDIR
 .PHONY: build_docker_image
 build_docker_image:
 	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
-	cat ./dockerfiles/Dockerfile.dev | docker build ${DOCKER_BUILD_ARGS} -t $(DEV_DOCKER_IMAGE_NAME) -
+	cat ./dockerfiles/Dockerfile.dev | docker build ${DOCKER_BUILD_ARGS} --build-arg=GO_VERSION -t $(DEV_DOCKER_IMAGE_NAME) -
 
 # build docker image having the linting tools (dockerfiles/Dockerfile.lint)
 .PHONY: build_linter_image
 build_linter_image:
 	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
-	cat ./dockerfiles/Dockerfile.lint | docker build ${DOCKER_BUILD_ARGS} -t $(LINTER_IMAGE_NAME) -
+	cat ./dockerfiles/Dockerfile.lint | docker build ${DOCKER_BUILD_ARGS} --build-arg=GO_VERSION -t $(LINTER_IMAGE_NAME) -
 
 .PHONY: build_cross_image
 build_cross_image:
 	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
-	cat ./dockerfiles/Dockerfile.cross | docker build ${DOCKER_BUILD_ARGS} -t $(CROSS_IMAGE_NAME) -
+	cat ./dockerfiles/Dockerfile.cross | docker build ${DOCKER_BUILD_ARGS} --build-arg=GO_VERSION -t $(CROSS_IMAGE_NAME) -
 
 .PHONY: build_shell_validate_image
 build_shell_validate_image:
 	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
-	cat ./dockerfiles/Dockerfile.shellcheck | docker build -t $(VALIDATE_IMAGE_NAME) -
+	cat ./dockerfiles/Dockerfile.shellcheck | docker build --build-arg=GO_VERSION -t $(VALIDATE_IMAGE_NAME) -
 
 .PHONY: build_binary_native_image
 build_binary_native_image:
 	# build dockerfile from stdin so that we don't send the build-context; source is bind-mounted in the development environment
-	cat ./dockerfiles/Dockerfile.binary-native | docker build -t $(BINARY_NATIVE_IMAGE_NAME) -
+	cat ./dockerfiles/Dockerfile.binary-native | docker build --build-arg=GO_VERSION -t $(BINARY_NATIVE_IMAGE_NAME) -
 
 .PHONY: build_e2e_image
 build_e2e_image:
-	docker build -t $(E2E_IMAGE_NAME) --build-arg VERSION=$(VERSION) --build-arg GITCOMMIT=$(GITCOMMIT) -f ./dockerfiles/Dockerfile.e2e .
+	docker build -t $(E2E_IMAGE_NAME) --build-arg=GO_VERSION --build-arg VERSION=$(VERSION) --build-arg GITCOMMIT=$(GITCOMMIT) -f ./dockerfiles/Dockerfile.e2e .
 
 DOCKER_RUN_NAME_OPTION := $(if $(DOCKER_CLI_CONTAINER_NAME),--name $(DOCKER_CLI_CONTAINER_NAME),)
 DOCKER_RUN := docker run --rm $(ENVVARS) $(DOCKER_CLI_MOUNTS) $(DOCKER_RUN_NAME_OPTION)

dockerfiles/Dockerfile.binary-native

@@ -1,4 +1,6 @@
-FROM    golang:1.12.7-alpine
+ARG GO_VERSION=1.12.7
+
+FROM    golang:${GO_VERSION}-alpine
 
 RUN     apk add -U git bash coreutils gcc musl-dev
 

dockerfiles/Dockerfile.cross

@@ -1,4 +1,6 @@
-FROM	dockercore/golang-cross:1.12.7
+ARG GO_VERSION=1.12.7
+
+FROM	dockercore/golang-cross:${GO_VERSION}
 ENV     DISABLE_WARN_OUTSIDE_CONTAINER=1
 WORKDIR /go/src/github.com/docker/cli
 COPY    . .

dockerfiles/Dockerfile.dev

@@ -1,4 +1,6 @@
-FROM    golang:1.12.7-alpine
+ARG GO_VERSION=1.12.7
+
+FROM    golang:${GO_VERSION}-alpine
 
 RUN     apk add -U git make bash coreutils ca-certificates curl
 

dockerfiles/Dockerfile.lint

@@ -1,4 +1,6 @@
-FROM    golang:1.12.7-alpine
+ARG GO_VERSION=1.12.7
+
+FROM    golang:${GO_VERSION}-alpine
 
 RUN     apk add -U git