> We recommend that, the frontend and the backend communicate through sockets, and named pipes on Windows, instead of
> HTTP. This prevents port collision with any other running application or container running
> on the host. Also, some Docker Desktop users are running in constrained environments where they
> can't open ports on their machines. When choosing the language and framework for your backend, make sure it
> supports sockets connection.

{{< tabs group="lang" >}}
{{< tab name="Go" >}}

```go
package main

import (
	"flag"
	"log"
	"net"
	"net/http"
	"os"

	"github.com/labstack/echo"
	"github.com/sirupsen/logrus"
)

func main() {
	var socketPath string
	flag.StringVar(&socketPath, "socket", "/run/guest/volumes-service.sock", "Unix domain socket to listen on")
	flag.Parse()

	os.RemoveAll(socketPath)

	logrus.New().Infof("Starting listening on %s\n", socketPath)
	router := echo.New()
	router.HideBanner = true

	startURL := ""

	ln, err := listen(socketPath)
	if err != nil {
		log.Fatal(err)
	}
	router.Listener = ln

	router.GET("/hello", hello)

	log.Fatal(router.Start(startURL))
}

func listen(path string) (net.Listener, error) {
	return net.Listen("unix", path)
}

func hello(ctx echo.Context) error {
	return ctx.JSON(http.StatusOK, HTTPMessageBody{Message: "hello world"})
}

type HTTPMessageBody struct {
	Message string
}
```

{{< /tab >}}
{{< tab name="Node" >}}

> [!IMPORTANT]
>
> We don't have a working example for Node yet. [Fill out the form](https://docs.google.com/forms/d/e/1FAIpQLSdxJDGFJl5oJ06rG7uqtw1rsSBZpUhv_s9HHtw80cytkh2X-Q/viewform?usp=pp_url&entry.25798127=Node)
> and let us know if you'd like a sample for Node.

{{< /tab >}}
{{< tab name="Python" >}}

> [!IMPORTANT]
>
> We don't have a working example for Python yet. [Fill out the form](https://docs.google.com/forms/d/e/1FAIpQLSdxJDGFJl5oJ06rG7uqtw1rsSBZpUhv_s9HHtw80cytkh2X-Q/viewform?usp=pp_url&entry.25798127=Python)
> and let us know if you'd like a sample for Python.

{{< /tab >}}
{{< tab name="Java" >}}

> [!IMPORTANT]
>
> We don't have a working example for Java yet. [Fill out the form](https://docs.google.com/forms/d/e/1FAIpQLSdxJDGFJl5oJ06rG7uqtw1rsSBZpUhv_s9HHtw80cytkh2X-Q/viewform?usp=pp_url&entry.25798127=Java)
> and let us know if you'd like a sample for Java.

{{< /tab >}}
{{< tab name=".NET" >}}

> [!IMPORTANT]
>
> We don't have a working example for .NET. [Fill out the form](https://docs.google.com/forms/d/e/1FAIpQLSdxJDGFJl5oJ06rG7uqtw1rsSBZpUhv_s9HHtw80cytkh2X-Q/viewform?usp=pp_url&entry.25798127=.Net)
> and let us know if you'd like a sample for .NET.

{{< /tab >}}
{{< /tabs >}}

## Adapt the Dockerfile

> [!NOTE]
>
> When using the `docker extension init`, it creates a `Dockerfile` that already contains what is needed for a Go backend.

{{< tabs group="lang" >}}
{{< tab name="Go" >}}

To deploy your Go backend when installing the extension, you need first to configure the `Dockerfile`, so that it:
- Builds the backend application
- Copies the binary in the extension's container filesystem
- Starts the binary when the container starts listening on the extension socket

> [!TIP]
> 
> To ease version management, you can reuse the same image to build the frontend, build the
backend service, and package the extension.

```dockerfile
# syntax=docker/dockerfile:1
FROM node:17.7-alpine3.14 AS client-builder
# ... build frontend application

# Build the Go backend
FROM golang:1.17-alpine AS builder
ENV CGO_ENABLED=0
WORKDIR /backend
COPY vm/go.* .
RUN --mount=type=cache,target=/go/pkg/mod \
    --mount=type=cache,target=/root/.cache/go-build \
    go mod download
COPY vm/. .
RUN --mount=type=cache,target=/go/pkg/mod \
    --mount=type=cache,target=/root/.cache/go-build \
    go build -trimpath -ldflags="-s -w" -o bin/service

FROM alpine:3.15
# ... add labels and copy the frontend application

COPY --from=builder /backend/bin/service /
CMD /service -socket /run/guest-services/extension-allthethings-extension.sock
```

{{< /tab >}}
{{< tab name="Node" >}}