Defer execution order in Go - Mini Project: Build & Apply

Defer Execution Order in Go

📖 Scenario: Imagine you are writing a Go program that needs to clean up resources in a specific order after some operations. You want to learn how defer statements work and how their execution order is managed.

🎯 Goal: Build a Go program that uses multiple defer statements and prints messages to show the order in which deferred functions execute.

📋 What You'll Learn

Create a main function

Use multiple defer statements with print messages

Understand and demonstrate the LIFO (last-in, first-out) order of defer execution

Print the messages to show the order clearly

💡 Why This Matters

🌍 Real World

In real programs, defer is used to ensure resources like files or network connections are properly closed even if errors occur.

💼 Career

Understanding defer is important for writing clean, safe Go code especially in backend development, system programming, and cloud services.

1

Create the main function and initial print

Write a main function in Go that prints "Start of main".

Go

package main

func main() {
    // Your code here
}

Hint

Use func main() to define the main function and println to print the message.

2

Add two defer statements with print messages

Inside the main function, add two defer statements that print "First defer" and "Second defer" respectively.

Go

package main

func main() {
    println("Start of main")
    // Your code here
}

Hint

Use defer println("message") to add deferred print statements.

3

Add a final print statement after defer statements

After the two defer statements, add a print statement that prints "End of main" inside the main function.

Go

package main

func main() {
    println("Start of main")
    defer println("First defer")
    defer println("Second defer")
    // Your code here
}

Hint

Just add println("End of main") after the defer statements.

4

Run the program and observe the output

Run the program and print the output to see the order of execution of the print statements and deferred functions.

Go

package main

func main() {
    println("Start of main")
    defer println("First defer")
    defer println("Second defer")
    println("End of main")
}

// Run the program to see the output

Hint

Run the program using go run and observe that deferred functions run in reverse order.