Your First Go Program

Every Go project lives in a module — a folder with a go.mod file that names the project and records its dependencies. Create one:

mkdir hello
cd hello
go mod init example.com/hello

That generates go.mod:

module example.com/hello

go 1.23.4

The module path (example.com/hello) is just a unique name; it only needs to be a real URL if you later publish the code.

Now create main.go in the same folder:

package main

import "fmt"

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

And run it:

go run .

Expected output

Hello, world!

Line by line:

• package main — every Go file belongs to a package. The special package main produces a runnable program (rather than a library).
• import "fmt" — brings in the standard library's formatting package, which handles printing.
• func main() — the program's entry point. It takes no arguments and returns nothing.
• fmt.Println(...) — prints its arguments followed by a newline. The capital P matters: in Go, names starting with an uppercase letter are exported (visible outside their package).

Common mistakes

• Putting the opening brace on its own line. Go inserts semicolons automatically at line ends, so func main() followed by { on the next line is a compile error.
• Importing a package and not using it — "fmt" imported and not used is a compile error, not a warning.

Practice

Change the program to print your own name on one line and your favorite language on the next.

package main

import "fmt"

func main() {
    fmt.Println("Ada")
    fmt.Println("Go")
}