LearnBuildbeginner12 min

Your first Go program

Packages, a function, a loop — and one command to run it.

You will build

A program that prints a greeting and the squares of 1 through 5.

You will learn

package main, func main(), importing fmt, a function, and a for loop.

Open the full project in VS Code

Prerequisites

Go installed locally to run it, or read along.

Go is deliberately small — few keywords, fast builds, one obvious way to do most things. Every program lives in a package and starts at func main().

project · go-hello Open in Code

main.goGO

1package main
2 
3import "fmt"
4 
5func square(n int) int {
6	return n * n
7}
8 
9func main() {
10	fmt.Println("Hello, Go")
11	for i := 1; i <= 5; i++ {
12		fmt.Printf("%d squared is %d\n", i, square(i))
13	}
14}

Hello, Go — open it in Code

Concept · go/functions

Catalog

Functions in Go

Parameter and return types come after the name: `func square(n int) int`. The `main` package with a `main` function is what `go run` executes.

func square(n int) int {
	return n * n
}

bash

$go run main.go
Hello, Go
1 squared is 1
2 squared is 4
3 squared is 9
4 squared is 16
5 squared is 25

Milestone

You ran your first Go program.

A package, an import, a function, and a loop — and a single command, `go run`, to build and execute it.

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