Building Go Programs

Use go build to produce an executable that you can run again without recompiling the source each time.

Inside an executable module, go build compiles the main package and writes an executable file. Name the output explicitly with go build -o app . (on Windows use a filename such as app.exe). Then run the built file using the shell.

go run is convenient for development; go build creates an artifact you can distribute for a compatible operating system and architecture. A Go executable is not automatically compatible with every platform.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

Build and execute

go build -o calculator .
./calculator

On Windows, build with go build -o calculator.exe . and run .\calculator.exe in PowerShell.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	total := 12 + 8
	fmt.Println("Total:", total)
}

Output

Total: 20

The compiler checks the program and embeds the compiled instructions in an executable. Running that file starts main() and prints the same output as the development command.

• go build and go run serve different purposes; the former does not automatically execute its artifact.
• Do not assume the built binary has the same name or extension on every operating system.

Build the example using go build -o calculator ., run the resulting executable, then modify the source and observe that the old binary stays unchanged until rebuilt.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Building Go Programs in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.