Merge pull request #907 from infosiftr/golang-tweaks

Unroll "golang:onbuild", update to 1.8, and use "%%IMAGE%%"

golang/content.md

@@ -13,13 +13,17 @@ Go (a.k.a., Golang) is a programming language first developed at Google. It is a
 The most straightforward way to use this image is to use a Go container as both the build and runtime environment. In your `Dockerfile`, writing something along the lines of the following will compile and run your project:
 
 ```dockerfile
-FROM golang:1.6-onbuild
+FROM %%IMAGE%%:1.8
+
+WORKDIR /go/src/app
+COPY . .
+
+RUN go-wrapper download   # "go get -d -v ./..."
+RUN go-wrapper install    # "go install -v ./..."
+
+CMD ["go-wrapper", "run"] # ["app"]
 ```
 
-This image includes multiple `ONBUILD` triggers which should cover most applications. The build will `COPY . /go/src/app`, `RUN go get -d -v`, and `RUN go install -v`.
-
-This image also includes the `CMD ["app"]` instruction which is the default command when running the image without arguments.
-
 You can then build and run the Docker image:
 
 ```console
@@ -27,20 +31,20 @@ $ docker build -t my-golang-app .
 $ docker run -it --rm --name my-running-app my-golang-app
 ```
 
-*Note:* the default command in `%%REPO%%:onbuild` is actually `go-wrapper run`, which includes `set -x` so the binary name is printed to stderr on application startup. If this behavior is undesirable, then adding `CMD ["app"]` (or `CMD ["myapp"]` if a [Go custom import path](https://golang.org/s/go14customimport) is in use) will silence it by running the built binary directly.
+*Note:* `go-wrapper run` includes `set -x` so the binary name is printed to stderr on application startup. If this behavior is undesirable, then switching to `CMD ["app"]` (or `CMD ["myapp"]` if a [Go custom import path](https://golang.org/s/go14customimport) is in use) will silence it by running the built binary directly.
 
 ## Compile your app inside the Docker container
 
 There may be occasions where it is not appropriate to run your app inside a container. To compile, but not run your app inside the Docker instance, you can write something like:
 
 ```console
-$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 go build -v
+$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:1.8 go build -v
 ```
 
 This will add your current directory as a volume to the container, set the working directory to the volume, and run the command `go build` which will tell go to compile the project in the working directory and output the executable to `myapp`. Alternatively, if you have a `Makefile`, you can run the `make` command inside your container.
 
 ```console
-$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash -c make
+$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:1.8 make
 ```
 
 ## Cross-compile your app inside the Docker container
@@ -48,13 +52,13 @@ $ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash -c
 If you need to compile your application for a platform other than `linux/amd64` (such as `windows/386`):
 
 ```console
-$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp -e GOOS=windows -e GOARCH=386 golang:1.6 go build -v
+$ docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp -e GOOS=windows -e GOARCH=386 %%IMAGE%%:1.8 go build -v
 ```
 
 Alternatively, you can build for multiple platforms at once:
 
 ```console
-$ docker run --rm -it -v "$PWD":/usr/src/myapp -w /usr/src/myapp golang:1.6 bash
+$ docker run --rm -it -v "$PWD":/usr/src/myapp -w /usr/src/myapp %%IMAGE%%:1.8 bash
 $ for GOOS in darwin linux; do
 >   for GOARCH in 386 amd64; do
 >     go build -v -o myapp-$GOOS-$GOARCH