Scaffold a Simple Go Project

For this exercise, we’ll create a Go project called “my-greeter”.

Create the project

Create a directory for the project and cd into it:

mkdir my-greeter

cd my-greeter

When you import packages from other modules, those dependencies are managed through your code’s module. This is defined by a go.mod file that will track those modules. The go.mod file must stay with your project, including in your source code repository (if applicable).

When you enable dependency tracking, you should provide a name that reflects the module your code will be in. For actual development, this will typically be the repository location where your source code will be kept. For example, the module path might be github.com/mymodule. If you plan to publish your module for others to use, the module path must be a location from which Go tools can download your module. Learn more here: Managing dependencies.

For this example, just use example/my-greeter:

go mod init example/my-greeter

Output:

go: creating new go.mod: module example/my-greeter

This will create a go.mod file with contents similar to this:

module example/my-greeter

go 1.27.1

Add a program

Next, create a greeter.go file and paste this content into it:

package main

import "fmt"

func main() {
	fmt.Println("Greetings!")
}

In this code:

• A main package is declared. A package provides a way to group functions.
• The fmt package is imported. It provides functions for formatting text, including printing to the console. This package is part of the standard library, so it doesn’t need to be added as an external package.
• A main() function is implemented, providing an entry point into the program.

Run the file:

go run greeter.go

Output:

Greetings!

Call an external package

We’ll add a “quote” package and call a function in it.

1. Go to pkg.go.dev and search for a “quote” package.
2. Locate and click on v1 of the rsc.io/quote package. You’ll see a list of functions available in the package. (We’ll be using the Go() function)

Update greeter.go so that it looks like this:

package main

import (
	"fmt"

	"rsc.io/quote"
)

func main() {
	fmt.Println("Greetings! Here's a quote:")

	fmt.Println(quote.Go())
}

You’ll notice a couple of changes:

1. We’ve added an import for the external “quote” package, and
2. We’re calling the Go() function in that package.

But this alone is not adequate. If we try to run the project now, we get an error:

go run greeter.go

Output:

greeter.go:6:2: no required module provides package rsc.io/quote; to add it:
	go get rsc.io/quote

This is because we’re attempting to import a package that hasn’t been added to the project. Let’s fix it:

go get rsc.io/quote

Output:

go: downloading rsc.io/quote v1.5.2
go: downloading rsc.io/sampler v1.3.0
go: downloading golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c
go: added golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c
go: added rsc.io/quote v1.5.2
go: added rsc.io/sampler v1.3.0

The go get command adds the quote package to the project, along with references to additional packages that quote depends on.

To accomplish this, the go.mod file gets updated:

module example/my-greeter

go 1.27.1

require (
	rsc.io/quote v1.5.2
	golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c // indirect
	rsc.io/sampler v1.3.0 // indirect
)

And a new go.sum file is added:

golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c h1:qgOY6WgZOaTkIIMiVjBQcw93ERBE4m30iBm00nkL0i8=
golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
rsc.io/quote v1.5.2 h1:w5fcysjrx7yqtD/aO+QwRjYZOKnaM9Uh2b40tElTs3Y=
rsc.io/quote v1.5.2/go.mod h1:LzX7hefJvL54yjefDEDHNONDjII0t9xZLPXsUe+TKr0=
rsc.io/sampler v1.3.0 h1:7uVkIFmeBqHfdjD+gZwtXXI+RODJ2Wc4O7MPEh/QiW4=
rsc.io/sampler v1.3.0/go.mod h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=

Now, our program works:

go run greeter.go

Output:

Greetings! Here's a quote:
Don't communicate by sharing memory, share memory by communicating.

References can also be refreshed at any time with this:

go mod tidy

If we run it now, we see that go.mod gets reorganized a bit:

module example/my-greeter

go 1.27.1

require rsc.io/quote v1.5.2

require (
	golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c // indirect
	rsc.io/sampler v1.3.0 // indirect
)

Finally, we can generate a standalone executable with this:

go build

This produces a statically linked binary:

file my-greeter

Output:

my-greeter: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked,
Go BuildID=L3BxWSF4oD-DWwXKLm72/Bz3veI-EabZcdQArLtVF/DxUbGthXdYMhCtveD6dv/wnXe8ZvLnaBOp751-Odv,
BuildID[sha1]=611276cb88c0cd80efc9142e96779c266816d23f, with debug_info, not stripped

And we can run it directly:

./my-greeter

Output:

Greetings! Here's a quote:
Don't communicate by sharing memory, share memory by communicating.