In this example, we start the tr '[:lower:] [:upper:]' process
in a container and we set its STDIN to a strings.Reader and set
its STDOUT to os.Stdout.
The tr invocation will convert passed stream to uppercase.
To run this example:
$ docker pull busybox
$ go run main.go
HELLO WORLD
FROM
CONTAINER
> cl, _ := docker.NewClientFromEnv()
> d := dexec.Docker{cl}
>
> m, _ := dexec.ByCreatingContainer(docker.CreateContainerOptions{
> Config: &docker.Config{Image: "busybox"}})
>
< cmd := exec.Command("tr", "[:lower:]", "[:upper:]")
> cmd := d.Command(m, "tr", "[:lower:]", "[:upper:]")