> ## Documentation Index
> Fetch the complete documentation index at: https://docs.codecrafters.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Go

> Learn how to solve CodeCrafters challenges in Go

<Note>
  **New to Go?** We recommend checking out [Go by Example](https://gobyexample.com/) to get up to speed.
</Note>

## Local development

To run the code for your challenge locally, you'll need `go` installed. Our test runners use `go` version `1.19` (as of November 2023).

The script for your challenge (like `./your_bittorrent.sh`) will automatically compile your code using `go build` before executing it.

## File structure

* The files for your solution are placed in the `app/` directory.
* `app/main.go` contains the `main` function, which is what the test runner executes.

## Adding more files

You can add more files and directories to `app/`. The test runner will include them when compiling your code.

For example, if you added a file at `app/foo.go`, you could use it like so:

<CodeGroup>
  ```go app/main.go theme={null}
  package main

  func main() {
      foo() // Uses the foo function from foo.go
  }
  ```

  ```go app/foo.go theme={null}
  package main

  func foo() {
      println("Hello world!")
  }
  ```
</CodeGroup>

All files in `app/` must have a `package main` declaration at the top of the file. If you want to extract files into a different package,
you can create a new folder in `app/` and add the `package` declaration to the top of each file in that folder.

Let's say you wanted to extract `foo.go` into the `bar` package. You'd move `foo.go` into the `app/bar` and add the relevant `package` declaration to the top of `foo.go`:

<CodeGroup>
  ```go app/bar/foo.go theme={null}
  package bar

  func foo() {
      println("Hello world!")
  }
  ```

  ```go app/main.go theme={null}
  package main

  import "github.com/codecrafters-io/dns-server-starter-go/app/bar" // Adjust this based on the package name in go.mod

  func main() {
      bar.foo() // Uses the foo function from app/bar/foo.go
  }
  ```
</CodeGroup>

Note that you'll need to update the import statement in `main.go` to use the new package name (Example: `github.com/codecrafters-io/dns-server-starter-go/app/bar`). You'll
find the first part of the package name in `go.mod`.

## Adding dependencies

You can add dependencies to your project by adding them to your `go.mod` file. You can use the `go get` command for this.

For example, to add the `github.com/spf13/cobra` library, you can run the following command:

```bash theme={null}
$ go get github.com/spf13/cobra

# Output:
#
# go: downloading github.com/spf13/cobra v1.8.0
# go: downloading github.com/inconshreveable/mousetrap v1.1.0
# go: added github.com/spf13/cobra v1.8.0
```

This'll add the following line to your `go.mod` file:

```go theme={null}
require github.com/spf13/cobra v1.1.3
```

It'll also make changes to your `go.sum` file.

When you push your code next, the runner will automatically download the dependency.

You can use the dependency in your code like so:

<CodeGroup>
  ```go app/main.go theme={null}
  package main

  import (
      "github.com/spf13/cobra"
  )

  func main() {
      var rootCmd = &cobra.Command{
          Use:   "test",
          Short: "test",
          Run: func(cmd *cobra.Command, args []string) {
              // Do Stuff Here
          },
      }

      rootCmd.Execute()
  }
  ```
</CodeGroup>