Golang docker directly

golang-docker-directly.go

// $ go run golang-docker-directly.go && docker run -it --rm golang-docker-directly
package main

import (
	"archive/tar"
	"bytes"
	"fmt"
	"log"
	"os/exec"
)

func createContext() (*bytes.Buffer, error) {
	// Create a buffer to write our archive to.
	buf := new(bytes.Buffer)

	// Create a new tar archive.
	tw := tar.NewWriter(buf)

	// Add some files to the archive.
	var files = []struct {
		Name, Body string
	}{
		{"Dockerfile", "FROM busybox\nADD gopher.txt /\nCMD cat /gopher.txt"},
		{"gopher.txt", "Gopher names:\nGeorge\nGeoffrey\nGonzo\n"},
	}
	for _, file := range files {
		hdr := &tar.Header{
			Name: file.Name,
			Mode: 0600,
			Size: int64(len(file.Body)),
		}
		if err := tw.WriteHeader(hdr); err != nil {
			return nil, err
		}
		if _, err := tw.Write([]byte(file.Body)); err != nil {
			return nil, err
		}
	}
	// Make sure to check the error on Close.
	if err := tw.Close(); err != nil {
		return nil, err
	}

	return buf, nil
}

func build(name string, context *bytes.Buffer) error {
	cmd := exec.Command("docker", "build", "-t", name, "-")

	// Open the tar archive for reading.
	cmd.Stdin = bytes.NewReader(context.Bytes())
	var out bytes.Buffer
	cmd.Stdout = &out

	err := cmd.Run()
	if err != nil {
		return err
	}

	fmt.Println(out.String())
	return nil
}

func main() {
	context, err := createContext()
	if err != nil {
		log.Fatal(err)
	}

	err = build("golang-docker-directly", context)
	if err != nil {
		log.Fatal(err)
	}

}