Creating and Running .go Files

Write your Go code in a text editor and save the file with a .go extension. Save the file using the UTF-8 character encoding.

sample_greet.go

package main

import "fmt"

func main() {
	name := "Kiryu Kazuma"
	age := 27

	fmt.Printf("Hello, %s!\n", name)
	fmt.Printf("Age: %d\n", age)

	if age >= 20 {
		fmt.Println("Adult.")
	} else {
		fmt.Println("Minor.")
	}
}

The first line, package main, indicates that this file is an executable program. The second line, import "fmt", imports the package that provides standard output and other functionality. Execution begins from the main function, which is the entry point of the program.

You can write comments (notes) in a .go file. Comments are ignored by the compiler, so they are useful for leaving descriptions or notes about the code.

sample_comments.go

package main

import "fmt"

/*
  The following is the main function.
  This is the entry point of the program.
*/
func main() {
	name := "Majima Goro"

	// Displays a greeting message.
	fmt.Printf("Hello, %s!\n", name)
}

This produces the following output:

go run sample_comments.go
Hello, Majima Goro!

In Go, a // comment written immediately before a function, type, or variable is treated as a documentation comment. It is a good habit to write comments for exported symbols.

Run directly with go run

The go run command compiles and runs in a single step. It is convenient when you want to try out code quickly.

go run greet.go
Hello, Kiryu Kazuma!
Age: 27
Adult.

Build with go build and then run

The go build command generates an executable file. The generated executable can run even in environments where Go is not installed.

go build greet.go

When the build succeeds, an executable file is generated in the current directory. If no error message is displayed, the build was successful. Run it with ./.

./greet
Hello, Kiryu Kazuma!
Age: 27
Adult.

To check the version, use the following command.

go version

A .go file is simply a plain text file. You can create one by writing Go code in a text editor and saving it with a .go extension. No special tools are needed.

There are two ways to run Go code. go run filename.go compiles and runs at once, which is convenient when you want to try code quickly. On the other hand, go build filename.go generates an executable, making it suitable for distribution or use in production environments.

There are two types of comments: single-line comments (//) and multi-line comments (/* */). In Go, single-line comments are used almost exclusively.

For information on installing Go, see Setup.