Packages and Modules

Packages group Go source files; modules record import paths, the minimum Go version, and external dependencies.

Every Go source file belongs to a package. A module groups packages and records their import path and dependencies in go.mod.

Start a module in the project directory. The go directive sets the minimum Go version required to build it.

Create go.mod with the module path used by packages that import this code:

OUTPUT

$ go mod init example.com/hello

module example.com/hello
 
go 1.26

Put related files in a package directory. A name that starts with an uppercase letter is exported and can be used by another package. This source is greeting/greeting.go:

package greeting
 
func Hello(name string) string {
    return "Hello, " + name
}

Import the package by its module path followed by the package directory. This source is main.go:

package main
 
import (
    "fmt"
    "example.com/hello/greeting"
)
 
func main() {
    fmt.Println(greeting.Hello("Gopher"))
}

In production

Use a module path your team controls. Run go mod tidy after changing imports, then commit go.mod and any generated go.sum so builds can verify declared dependencies.

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