_content/doc/tutorial/getting-started.html

<!--{
    "Title": "Tutorial: Get started with Go",
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}-->

<p>
  In this tutorial, you'll get a brief introduction to Go programming. Along the
  way, you will:
</p>

<ul>
  <li>Install Go (if you haven't already).</li>
  <li>Write some simple "Hello, world" code.</li>
  <li>Use the <code>go</code> command to run your code.</li>
  <li>
    Use the Go package discovery tool to find packages you can use in your own
    code.
  </li>
  <li>Call functions of an external module.</li>
</ul>

<aside class="Note">
  <strong>Note:</strong> For other tutorials, see
  <a href="/doc/tutorial/index.html">Tutorials</a>.
</aside>

<h2 id="prerequisites">Prerequisites</h2>

<ul>
  <li>
    <strong>Some programming experience.</strong> The code here is pretty
    simple, but it helps to know something about functions.
  </li>
  <li>
    <strong>A tool to edit your code.</strong> Any text editor you have will
    work fine. Most text editors have good support for Go. The most popular are
    VSCode (free), GoLand (paid), and Vim (free).
  </li>
  <li>
    <strong>A command terminal.</strong> Go works well using any terminal on
    Linux and Mac, and on PowerShell or cmd in Windows.
  </li>
</ul>

<h2 id="install">Install Go</h2>

<p>Just use the <a href="/doc/install">Download and install</a> steps.</p>

<h2 id="code">Write some code</h2>

<p>
  Get started with Hello, World.
</p>

<ol>
  <li>
    Open a command prompt and cd to your home directory.

    <p>
      On Linux or Mac:
    </p>

    <pre>
cd
</pre
    >

    <p>
      On Windows:
    </p>

    <pre>
cd %HOMEPATH%
</pre
    >
  </li>

  <li>
    Create a hello directory for your first Go source code.

    <p>
      For example, use the following commands:
    </p>

    <pre>
mkdir hello
cd hello
</pre
    >
  </li>

  <li>
    Enable dependency tracking for your code.

    <p>
      When your code imports packages contained in other modules, you manage
      those dependencies through your code's own module. That module is defined
      by a go.mod file that tracks the modules that provide those packages. That
      go.mod file stays with your code, including in your source code
      repository.
    </p>

    <p>
      To enable dependency tracking for your code by creating a go.mod file, run
      the
      <a href="/ref/mod#go-mod-init"><code>go mod init</code></a> command,
        giving it the name of the module your code will be in. The name is the
        module's module path.</p>
    <p>In actual development, the module path will typically be the repository
        location where your source code will be kept. For example, the module
        path might be <code>github.com/mymodule</code>. If you plan to publish
        your module for others to use, the module path <em>must</em> be a
        location from which Go tools can download your module. For more about
        naming a module with a module path, see
        <a href="/doc/modules/managing-dependencies#naming_module">Managing
            dependencies</a>.
    </p>

      <p>For the purposes of this tutorial, just use
          <code>example/hello</code>.
    </p>

    <pre>
$ go mod init example/hello
go: creating new go.mod: module example/hello
</pre
    >
  </li>

  <li>
    <p>In your text editor, create a file hello.go in which to write your code.</p>
  </li>

  <li>
    <p>Paste the following code into your hello.go file and save the file.</p>

    <pre>
package main

import "fmt"

func main() {
    fmt.Println("Hello, World!")
}
</pre
    >

    <p>
      This is your Go code. In this code, you:
    </p>

    <ul>
      <li>
        Declare a <code>main</code> package (a package is a way to group
        functions, and it's made up of all the files in the same directory).
      </li>
      <li>
        Import the popular
        <a href="https://pkg.go.dev/fmt/"><code>fmt</code> package</a>,
        which contains functions for formatting text, including printing to the
        console. This package is one of the
        <a href="https://pkg.go.dev/std">standard library</a> packages you got
        when you installed Go.
      </li>
      <li>
        Implement a <code>main</code> function to print a message to the
        console. A <code>main</code> function executes by default when you run
        the <code>main</code> package.
      </li>
    </ul>
  </li>

  <li>
    <p>Run your code to see the greeting.</p>

    <pre>
$ go run .
Hello, World!
</pre
    >

    <p>
      The
      <a href="/cmd/go/#hdr-Compile_and_run_Go_program"
        ><code>go run</code></a> command
      is one of many <code>go</code> commands you'll use to get things done with
      Go. Use the following command to get a list of the others:
    </p>

    <pre>
$ go help
</pre
    >
  </li>
</ol>

<h2 id="call">Call code in an external package</h2>

<p>
  When you need your code to do something that might have been implemented by
  someone else, you can look for a package that has functions you can use in
  your code.
</p>

<ol>
  <li>
    Make your printed message a little more interesting with a function from an
    external module.

    <ol>
      <li>
        Visit pkg.go.dev and
        <a href="https://pkg.go.dev/search?q=quote"
          >search for a "quote" package</a
        >.
      </li>
      <li>
        In the search results, locate and click on the v1 of the <code>rsc.io/quote</code> package
        (it should be listed with the "Other major versions" of <code>rsc.io/quote/v4</code>).
      </li>
      <li>
        In the <strong>Documentation</strong> section, under <strong>Index</strong>, note the
        list of functions you can call from your code. You'll use the
        <code>Go</code> function.
      </li>
      <li>
        At the top of this page, note that package <code>quote</code> is
        included in the <code>rsc.io/quote</code> module.
      </li>
    </ol>

    <p>
      You can use the pkg.go.dev site to find published modules whose packages
      have functions you can use in your own code. Packages are published in
      modules -- like <code>rsc.io/quote</code> -- where others can use them.
      Modules are improved with new versions over time, and you can upgrade your
      code to use the improved versions.
    </p>
  </li>

  <li>
    In your Go code, import the <code>rsc.io/quote</code> package and add a call
    to its <code>Go</code> function.

    <p>
      After adding the highlighted lines, your code should include the
      following:
    </p>

    <pre>
package main

import "fmt"

<ins>import "rsc.io/quote"</ins>

func main() {
    <ins>fmt.Println(quote.Go())</ins>
}
</pre>
  </li>

  <li>
    Add new module requirements and sums.

    <p>
      Go will add the <code>quote</code> module as a requirement, as well as a
      go.sum file for use in authenticating the module. For more, see
      <a href="/ref/mod#authenticating">Authenticating modules</a> in the Go
      Modules Reference.
    </p>
    <pre>
$ go mod tidy
go: finding module for package rsc.io/quote
go: found rsc.io/quote in rsc.io/quote v1.5.2
</pre
    >
  </li>

  <li>
    Run your code to see the message generated by the function you're calling.

    <pre>
$ go run .
Don't communicate by sharing memory, share memory by communicating.
</pre
    >

    <p>
      Notice that your code calls the <code>Go</code> function, printing a
      clever message about communication.
    </p>

    <p>
      When you ran <code>go mod tidy</code>, it located and downloaded the
      <code>rsc.io/quote</code> module that contains the package you imported.
      By default, it downloaded the latest version -- v1.5.2.
    </p>
  </li>
</ol>

<h2 id="write-more">Write more code</h2>

<p>
  With this quick introduction, you got Go installed and learned some of the
  basics. To write some more code with another tutorial, take a look at
  <a href="/doc/tutorial/create-module.html">Create a Go module</a>.
</p>