Your first Go program

Time to write and run real Go. In this lesson you create a module, write a Hello World program in main.go, run it with go run, and build a standalone binary with go build — while learning what each line does.

Create a module

A Go project is a module, described by a go.mod file. Make an empty folder, open a terminal in it, and initialise the module:

mkdir hello
cd hello
go mod init example/hello

That command writes a small go.mod file recording the module path and the Go version:

module example/hello

go 1.24

The module path (example/hello) is just an identifier. For a project you plan to publish, you would use its repository path, such as github.com/you/hello.

Write main.go

Create a file named main.go next to go.mod and type in this complete, runnable program:

package main

import "fmt"

func main() {
	fmt.Println("Hello, World!")
}

That is a full Go program. Save the file — the next section runs it.

Understand each part

Every line above has a job:

• package main declares that this file belongs to the main package. A program you can run must have a main package; any other name produces a library instead of an executable.
• import "fmt" pulls in the standard library’s fmt package, which handles formatted input and output.
• func main() is the entry point. When you run the program, Go calls main first; when it returns, the program ends.
• fmt.Println(...) prints its argument followed by a newline.

Run it with go run

From the module folder, run the program with:

go run .

The . tells Go to build and run the package in the current directory. You will see:

Hello, World!

go run compiles to a temporary location and runs immediately — perfect while you are experimenting.

Build a binary with go build

When you want a file you can share or deploy, compile it instead:

go build

This produces an executable in the current folder — hello on macOS and Linux, hello.exe on Windows — named after the module. Run it directly:

./hello

The output is the same Hello, World!, but now it is a self-contained binary with no Go installation required to run it.

Common mistakes

• Wrong package name. If the first line is not package main, go run and go build will not create a runnable program.
• Missing the import. Using fmt.Println without import "fmt" fails to compile. Conversely, importing a package you never use is also an error.
• Running from the wrong folder. go run . and go build must run inside the module directory that holds go.mod and main.go.

Practice

Starting from the same module, change the program so it prints two lines: Hello, World! and then I am writing Go..

package main

import "fmt"

func main() {
	fmt.Println("Hello, World!")
	fmt.Println("I am writing Go.")
}

Summary

• A Go project is a module created with go mod init <path>.
• A runnable program needs package main and a func main entry point.
• Use go run . to run during development and go build to produce a binary.

Now that you can run code, learn how to store and use values with variables and types in Go. You can also revisit the full Go course index.