The Go Programming Language

10.3 The Package Declaration

A package declaration is required at the start of every Go source file. Its main purpose is to determine the default identifier for that package (called the package name) when it is imported by another package.

For example, every file of the math/rand package starts with package rand, so when you import this package, you can access its members as rand.Int, rand.Float64, and so on.

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    fmt.Println(rand.Int())
}

Conventionally, the package name is the last segment of the import path, and as a result, two packages may have the same name even though their import paths necessarily differ. For example, the packages whose import paths are math/rand and crypto/rand ...