A function is a block of statements which performs a specific task. A function is a well-organized and reusable code. It improves the code readability, maintainability and testability. The general function is:

func function_name( [parameter list] ) [return_types]
{
  body of the function
}

Declaring and calling functions

The function is declared using func the keyword.

func sayCheeze() {
  fmt.Println("Cheeeeeeeeeeeeze")
}

Calling the function is pretty easy.

sayCheeze()

package main

import "fmt"

func sayCheeze() {
    fmt.Println("Cheeeeeeeeeeeeze")
}

func main() {
    sayCheeze()
}

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You may pass input parameters

func addition(i int, j int) {
  fmt.Println(i + j)
}

We need to pass the declared number of parameters while calling the function.

addition(1, 2)

When two or more consecutive parameters have the same type we can omit the type from all but the last.

package main

import "fmt"

func addition(i, j, k int) {
    fmt.Println(i + j + k)
}

func main() {
    addition(10, 20, 30)
}

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You may define the return type of the function

func addition(i, j, k int) int {
   return i + j + k
}

sum := addition(1, 2, 3)

A function can return any number of results.

package main

import "fmt"

func addition(i, j int) (int, int, int) {
    return i, j, i + j
}

func main() {
    a, b, sum := addition(1, 2)
    fmt.Println(a, b, sum)
}

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Named return values

Go's return values may be named. The named return values are treated as locally defined variables in the function.

package main

import "fmt"

func division(i int) (quotient, remainder int) {
    quotient = i / 10
    remainder = i % 10
    return
}
func main() {
    quotient, remainder := division(125)
    fmt.Printf("Quotient: %d and Remainder: %d", quotient, remainder)
}

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Variadic functions

Variadic functions can be called with any number of trailing arguments. For example, fmt.Println is a common variadic function.

package main

import "fmt"

func total(nums ...int) (total int) {
    for _, i := range nums {
        total += i
    }
    return total
}

func main() {
    fmt.Println(total(1, 2, 3, 4, 5))
    fmt.Println(total(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))
}

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