New to Go? We recommend checking out Go by Example to get up to speed.

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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.

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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.

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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: 
package main

fun main() {
    foo() // Uses the foo function from foo.go
}
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: 
package bar

fun foo() {
    println("Hello world!")
}
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.

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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: 
$ 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: 
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: 
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()
}