Several files and packages

Split package main over several files in one folder; what the standard library offers without installing anything.

Runs in Zerethon IDE · Go 1.27 Official Go documentation ↗

main.go

package main

import "fmt"

func main() {
	fmt.Println(Area(3, 4))
	fmt.Println(Greeting)
}

geometry.go

package main

const Greeting = "shapes ok"

func Area(width, height int) int {
	return width * height
}

Output

12
shapes ok

Two files in the same folder: main.go (the entry) and geometry.go, both package main. No import is needed between them.

Run builds the entry together with every other .go file in its folder, so they form one program.
Files whose name starts with main or test_ are left out — each of them is a separate program with its own main().
There is no go.mod and no network: only the standard library can be imported (fmt, strings, sort, math, time, encoding/json, …). go get is not available.

Official references