A group of statements enclosed within a program that performs some specific task is known as a **function**.

A function may or may not include some parameters. It can take an argument as an *input* and return some *output* accordingly.

# Syntax

In the Go language, we declare a function by typing the **`func` keyword**. After typing in the `func` keyword, we have to write the name of our function. Following that, we list the parameters (if any are present), and then list the return type of the function being defined.

After declaring the function, we have to write the statements inside the curly braces `{}`.

**Golang** includes an existing function, `main()`, that exists in every independent program.

``` go
func myFunction(paramter1, paramter2,...) datatype {
    // Some statements
}
```



# Use

We use functions to divide our program into smaller, reusable pieces of code and improve our program's readability, maintainability, and testability.

# Code
## Example 1: Simple function

Let's create a function that takes two parameters and performs some operation between them.

package main

// fmt is short for format. this package implements
// formatted input and output operaitons.
import "fmt"

func subtract(num1 int, num2 int) {
	sub_total := 0
	sub_total = num1 - num2
	fmt.Println(sub_total)
}

func main() {
	subtract(50, 40)
}

## Explanation

The above code demonstrates how to subtract two numbers of `int` datatype. 

We have a function `subtract` that takes two arguments as parameters: `num1` and `num2`. The function body performs subtraction operations on those parameters.

We have a `main()` function that calls our `subtract()` function to execute it.

> Note: The `package main` tells the Go compiler that the package should compile as an executable program instead of a shared library.

## Example 2: Function with return statement

Let's implement a function that takes two parameters, performs some operation between them, and returns their output.

package main
import "fmt"

func subtract(num1 int, num2 int) int {
	sub_total := 0
	sub_total = num1 - num2
	return sub_total
}

func main() {
	sub := subtract(50, 40)
    fmt.Println(sub)
}

## Explanation

The above code represents how to print the result using the `return` statement. 

Function `subtract` performs the subtraction operation on two `int` type variables: `num1` and `num2`.

The `main()` body calls and executes that function to display the result.

How to create a function in Golang

Functions in Go are blocks of code for specific tasks. Define using func keyword with parameters, return type, and body within {}. Functions improve code readability and testability.