Chainguard Container for go

Container image for building Go applications.

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/go:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

Where possible, the Go Chainguard Image is built for compatibility with the Docker official image for Golang.

Unlike most other Chainguard images, the Go image contains a shell; namely, Bash. The reason for this is that this image is meant to be used as a build image, not a runtime image. The Go binary itself isn't very useful, so the Go Chainguard image contains Bash, along with tools like make and gcc, to allow users to build binaries.

The Go Chainguard Image uses the glibc implementation of the C standard library, while the Alpine version of the Golang official Docker Image uses musl. See our article on glibc vs. musl on Chainguard Academy for an overview of the differences between these implementations.

When using the Chainguard Go image, we advise to use shared linking and the glibc-dynamic runtime image as static linking of C/C++ code can often create dark matter and invade scanners. As an alternative, we recommend using the static image as the runtime image, as it still provides CA certs for TLS. If using go-msft-fips, we recommend using glibc-openssl-fips.

The examples in this README recommend executing Go binaries from one of our runtime Chainguard Images, such as the glibc-dynamic or static Chainguard Images. If using the static Chainguard Image, make sure to build your Go binary with static linking. In most cases, this requires running CGO_ENABLED=0 go build when building the binary. If dynamic linking is needed, use the glibc-dynamic Chainguard Image or the Go Chainguard Image to run your application.

In Go 1.20, we default to using the new GODEBUG settings of tarinsecurepath=0 and zipinsecurepath=0. These can be disabled by clearing the GODEBUG environment variable, or by setting them to 1.

Learn more about these settings in the Go release notes.

Getting Started

Example: CLI Application Using Multi-Stage Build

The following build demonstrates a command line application with support for flags and positional arguments. The application prints a modifiable greeting message and provides usage information if the wrong number of arguments are passed by a user or the user passes an unrecognized flag.

First, create a project folder and change the working directory to that folder:

mkdir -p ~/go-greeter && cd $_

Next, ,write a file defining our Go CLI application (main.go:

cat << 'EOF' > main.go
package main

import (
	"flag"
	"fmt"
	"log"
	"os"
)

func usage() {
	fmt.Fprintf(os.Stderr, "usage: hello [options] [name]\n")
	flag.PrintDefaults()
	os.Exit(2)
}

var (
	greeting = flag.String("g", "Hello", "Greet with `greeting`")
)

func main() {
	// Configure logging
	log.SetFlags(0)
	log.SetPrefix("hello: ")

	// Parse flags.
	flag.Usage = usage
	flag.Parse()

	// Parse and validate arguments.
	name := "Linky 🐙"
	args := flag.Args()
	if len(args) >= 2 {
		usage()
	}
	if len(args) >= 1 {
		name = args[0]
	}
	if name == "" { // hello '' is an error
		log.Fatalf("invalid name %q", name)
	}

	fmt.Printf("%s, %s!\n", *greeting, name)
}
EOF

Create a go.mod` file to list dependencies:

cat << 'EOF' > go.mod
module chainguard.dev/greet

go 1.19
EOF

Write a Dockerfile to define our image build:

cat << 'EOF' > Dockerfile
FROM cgr.dev/chainguard/go AS builder
COPY . /app
RUN cd /app && go build -o go-greeter .

FROM cgr.dev/chainguard/static
COPY --from=builder /app/go-greeter /usr/bin/
ENTRYPOINT ["/usr/bin/go-greeter"]
EOF

The Dockerfile uses a multi-stage build approach, compiling the application using the go Chainguard Image, then copying the binary to the static Chainguard Image for execution. Note that the static image requires that the Go binary be statically linked—if your application requires dynamic linking, consider using the glibc-dynamic Chainguard Image for your runtime (see the second example in this README).

Build the image, tagging it go-greeter:

docker build . -t go-greeter

Run the image:

docker run go-greeter

You should see output similar to the following:

Hello, Linky 🐙!

You can also pass in arguments that will be parsed by the Go CLI application:

docker run go-greeter -g Greetings "Chainguard user"

This will produce the following output:

Greetings, Chainguard user!

The application will also share usage instructions when prompted with the --help flag or when invalid flags are passed.

Because we used the static Chainguard Image as our runtime, the final image only requires a few megabytes on disk:

docker inspect go-greeter | jq -c 'first' | jq .Size | numfmt --to iec --format "%8.4f"

The final size, 3.5055M, is orders of magnitude smaller than it would be running the application using a Go image. However, if your application is dynamically linked to shared objects, consider using the glibc-dynamic Chainguard Image for your runtime or take extra steps to build your Go binary statically.

Example: Web Application

The following build demonstrates an application that's accessible by HTTP server. The application renders a simple message that changes based on the URI.

First, create a project folder and change the working directory to that folder:

mkdir -p ~/greet-server && cd $_

Next, write a main.go file defining our web application:

cat << 'EOF' > main.go
package main

import (
	"flag"
	"fmt"
	"html"
	"log"
	"net/http"
	"os"
	"runtime/debug"
	"strings"
)

func usage() {
	fmt.Fprintf(os.Stderr, "usage: helloserver [options]\n")
	flag.PrintDefaults()
	os.Exit(2)
}

var (
	greeting = flag.String("g", "Hello", "Greet with `greeting`")
	addr     = flag.String("addr", "0.0.0.0:8080", "address to serve")
)

func main() {
	// Parse flags.
	flag.Usage = usage
	flag.Parse()

	// Parse and validate arguments (none).
	args := flag.Args()
	if len(args) != 0 {
		usage()
	}

	// Register handlers. for greeting and version
	http.HandleFunc("/", greet)
	http.HandleFunc("/version", version)

	log.Printf("serving http://%s\n", *addr)
	log.Fatal(http.ListenAndServe(*addr, nil))
}

func version(w http.ResponseWriter, r *http.Request) {
	info, ok := debug.ReadBuildInfo()
	if !ok {
		http.Error(w, "no build information available", 500)
		return
	}

	fmt.Fprintf(w, "<!DOCTYPE html>\n<pre>\n")
	fmt.Fprintf(w, "%s\n", html.EscapeString(info.String()))
}

func greet(w http.ResponseWriter, r *http.Request) {
	name := strings.Trim(r.URL.Path, "/")
	if name == "" {
		name = "Linky 🐙"
	}

	fmt.Fprintf(w, "<!DOCTYPE html>\n")
	fmt.Fprintf(w, "%s, %s!\n", *greeting, html.EscapeString(name))
}
EOF

Next, write a go.mod file listing dependencies:

cat << 'EOF' > go.mod
module chainguard.dev/greet-server

go 1.19
EOF

Write a Dockerfile to define our image build:

cat << 'EOF' > Dockerfile
FROM cgr.dev/chainguard/go AS builder
COPY . /app
RUN cd /app && go build

FROM cgr.dev/chainguard/glibc-dynamic
COPY --from=builder /app/greet-server /usr/bin/

EXPOSE 8080

ENTRYPOINT ["/usr/bin/greet-server"]
EOF

The Dockerfile uses a multi-stage build approach, compiling the application using the go Chainguard Image, then copying the binary to the glibc-dynamic Chainguard Image to serve.

Build the image, tagging it greet-server:

docker build . -t greet-server

Run the image:

docker run -p 8080:8080 greet-server

Visit http://0.0.0.0:8080/ using a web browser on your host machine. You should see the following:

Hello, Linky 🐙!

Changes to the URI will be routed to the application. Try visiting http://0.0.0.0:8080/Chainguard%20Customer. You should see the following output:

Hello, Chainguard Customer!

The application will also share version information at http://0.0.0.0:8080/version.

If you're building a web application with Go, consider the nginx Chainguard Image for use as a reverse proxy.

Documentation and Resources

• Chainguard Academy: Getting Started with the Go Chainguard Image
• Video: Migrating a Dockerfile for a Go application to use Chainguard Images
• Blog Post: Statically Linking Go in 2022
• Blog Post: Building minimal and low CVE images for compiled languages
• Chainguard Academy: glibc vs. musl

What are Chainguard Containers?

Chainguard Containers are minimal container images that are secure by default.

In many cases, the Chainguard Containers tagged as :latest contain only an open-source application and its runtime dependencies. These minimal container images typically do not contain a shell or package manager. Chainguard Containers are built with Wolfi, our Linux undistro designed to produce container images that meet the requirements of a more secure software supply chain.

The main features of Chainguard Containers include:

• Minimal design, without unnecessary software bloat
• Daily builds to ensure container images are up-to-date with available security patches
• High quality build-time SBOMs attesting to the provenance of all artifacts within the image
• Verifiable signatures provided by Sigstore
• Reproducible builds with Cosign and apko (read more about reproducibility)

For cases where you need container images with shells and package managers to build or debug, most Chainguard Containers come paired with a -dev variant.

Although the -dev container image variants have similar security features as their more minimal versions, they feature additional software that is typically not necessary in production environments. We recommend using multi-stage builds to leverage the -dev variants, copying application artifacts into a final minimal container that offers a reduced attack surface that won’t allow package installations or logins.

Learn More

To better understand how to work with Chainguard Containers, please visit Chainguard Academy and Chainguard Courses.

In addition to Containers, Chainguard offers VMs and Libraries. Contact Chainguard to access additional products.

Trademarks

This software listing is packaged by Chainguard. The trademarks set forth in this offering are owned by their respective companies, and use of them does not imply any affiliation, sponsorship, or endorsement by such companies.