Go defer

Introduction

Go defer runs a function after the function completes.

Consider the following example: 

package main/* w  w  w  .j  a  v  a  2 s. com*/

import "fmt" 

func first() { 
    fmt.Println("1st") 
} 

func second() { 
    fmt.Println("2nd") 
} 

func main() { 
    defer second() 
    first() 
}

This program prints 1st followed by 2nd.

Basically, defer moves the call to second to the end of the function: 

func main() { 
    first() 
    second() 
}

defer is often used when resources need to be freed in some way.

For example, when we open a file, we need to make sure to close it later. With defer: 

f, _  := os.Open(filename) 
defer f.Close()



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