Developing a Go-Based CLI for AWS Elastic Beanstalk

Introduction
Prerequisites
Setup
Creating the CLI
Command Line Interface
Deploying the Application
Conclusion

Introduction

In this tutorial, we will develop a command-line interface (CLI) using the Go programming language to interact with AWS Elastic Beanstalk. Elastic Beanstalk is a service that simplifies the deployment and management of applications in the AWS cloud. By the end of this tutorial, you will be able to use your CLI to deploy applications to Elastic Beanstalk, manage environments, and perform other common tasks.

Prerequisites

Before starting this tutorial, you should have a basic understanding of the Go programming language and familiarity with concepts such as functions, data structures, and command-line interfaces. Additionally, you will need to have the following software installed:

Go (version 1.13 or higher)
AWS CLI (version 2 or higher)

Setup

To begin, make sure you have Go and AWS CLI installed and properly configured on your system. You can verify the installations by running the following commands in your terminal:

go version
aws --version

If both commands return the installed versions of Go and AWS CLI, you are ready to proceed with the next steps.

Creating the CLI

Create a new directory for your project and navigate to it:

```bash
mkdir my-elastic-beanstalk-cli
cd my-elastic-beanstalk-cli
```

Initialize a new Go module:

```bash
go mod init github.com/your-username/my-elastic-beanstalk-cli
```

Create a new Go file named main.go and open it in your preferred text editor.

Import the necessary Go packages:

```go
package main

import (
    "flag"
    "fmt"
    "os"
    "os/exec"
    "strings"
)
```

Define global variables to store AWS credentials:

```go
var (
    accessKey string
    secretKey string
    region    string
)
```

Command Line Interface

Now let’s create the CLI commands for deploying an application to Elastic Beanstalk and managing environments.

Add the following function to define flags for your CLI commands:

```go
func configureFlags() {
    flag.StringVar(&accessKey, "access-key", "", "AWS access key ID")
    flag.StringVar(&secretKey, "secret-key", "", "AWS secret access key")
    flag.StringVar(&region, "region", "us-west-1", "AWS region")
}
```

Next, define a function to deploy an application:

```go
func deployApp() {
    // Validate required flags
    if accessKey == "" || secretKey == "" {
        fmt.Println("Access key and secret key are required.")
        return
    }

    // Deploy the application
    cmd := exec.Command("eb", "deploy")
    cmd.Env = append(os.Environ(),
        fmt.Sprintf("AWS_ACCESS_KEY_ID=%s", accessKey),
        fmt.Sprintf("AWS_SECRET_ACCESS_KEY=%s", secretKey),
        fmt.Sprintf("AWS_REGION=%s", region),
    )
    out, err := cmd.CombinedOutput()
    if err != nil {
        fmt.Printf("Failed to deploy application: %v\n", err)
        return
    }
    fmt.Println(string(out))
}
```

Now, let’s create a function to manage environments:

```go
func manageEnv() {
    // Validate required flags
    if accessKey == "" || secretKey == "" {
        fmt.Println("Access key and secret key are required.")
        return
    }

    // Get environment details
    cmd := exec.Command("eb", "status")
    cmd.Dir = "./my-app" // Path to your application
    cmd.Env = append(os.Environ(),
        fmt.Sprintf("AWS_ACCESS_KEY_ID=%s", accessKey),
        fmt.Sprintf("AWS_SECRET_ACCESS_KEY=%s", secretKey),
        fmt.Sprintf("AWS_REGION=%s", region),
    )
    out, err := cmd.CombinedOutput()
    if err != nil {
        fmt.Printf("Failed to get environment details: %v\n", err)
        return
    }
    fmt.Println(string(out))
}
```

Finally, add the main function to handle CLI commands:

```go
func main() {
    // Parse command line flags
    configureFlags()
    flag.Parse()

    if flag.NArg() == 0 {
        fmt.Println("Please specify a command.")
        return
    }

    command := strings.ToLower(flag.Arg(0))
    switch command {
    case "deploy":
        deployApp()
    case "env":
        manageEnv()
    default:
        fmt.Println("Invalid command.")
    }
}
```

Deploying the Application

To deploy the application using your CLI, follow these steps:

Build the CLI executable:
```
```bash
go build -o ebcli
```
```

Run the CLI with the deploy command:

```bash
./ebcli deploy -access-key YOUR_ACCESS_KEY -secret-key YOUR_SECRET_KEY -region YOUR_REGION
```

Replace `YOUR_ACCESS_KEY`, `YOUR_SECRET_KEY`, and `YOUR_REGION` with your own AWS credentials and desired region.

After running the command, your application will be deployed to Elastic Beanstalk.

Conclusion

Congratulations! You have successfully developed a Go-based CLI for AWS Elastic Beanstalk. In this tutorial, you learned how to create CLI commands to deploy applications and manage environments. This CLI allows you to automate common tasks and streamline your development workflow. Remember to handle errors gracefully and enhance the CLI with additional features as needed.

Feel free to explore the AWS CLI and Elastic Beanstalk documentation to discover more functionality and possibilities for your CLI. Happy coding!

Published: 9 September 2019