Go Packages

In Go, packages are used to organize related code into separate namespaces and to promote code reuse. A package is a collection of Go source files in the same directory that are compiled together as a single unit.

To create a package in Go, you typically start by creating a new directory for your package and adding one or more Go source files to it. Each source file in the package should have a package declaration at the top of the file, which specifies the name of the package. For example, a simple package called "myutils" might look like this:

myutils/
├── math.go
└── string.go

math.go:

package myutils

func Add(x, y int) int {
    return x + y
}

func Subtract(x, y int) int {
    return x - y
}

string.go:

package myutils

func Reverse(s string) string {
    runes := []rune(s)
    for i, j := 0, len(runes)-1; i < len(runes)/2; i, j = i+1, j-1 {
        runes[i], runes[j] = runes[j], runes[i]
    }
    return string(runes)
}

In this example, the myutils package contains two source files, math.go and string.go, which both declare the myutils package using the package keyword. The math.go file contains two functions for adding and subtracting integers, while the string.go file contains a function for reversing a string.

Once you've created a package, you can use it in other Go programs by importing it with the import keyword. For example, to use the myutils package in a program, you would write:

package main

import (
    "fmt"
    "myutils"
)

func main() {
    x := 3
    y := 4
    fmt.Println(myutils.Add(x, y)) // prints "7"
    fmt.Println(myutils.Reverse("hello")) // prints "olleh"
}

In this example, the main function imports the myutils package with the import keyword and uses its Add and Reverse functions to perform some simple calculations. Note that the functions in the myutils package are accessed using the package name (myutils) followed by a dot (.) and the function name (Add or Reverse).