How to use multiple defer in go

GoHow-ToBeginner · 3 min read

How to Use Multiple defer Statements in Go

In Go, you can use multiple defer statements to delay function calls until the surrounding function returns. These deferred calls execute in last-in, first-out (LIFO) order, meaning the last defer added runs first.

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Syntax

The defer keyword is used before a function call to delay its execution until the surrounding function finishes. You can write multiple defer statements in one function.

defer functionCall(): Schedules functionCall() to run later.
Deferred calls run in reverse order of their appearance.

func example() {
    defer fmt.Println("First defer")
    defer fmt.Println("Second defer")
    fmt.Println("Function body")
}

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Example

This example shows three defer statements. They run in reverse order after the main function body finishes.

package main

import "fmt"

func main() {
    defer fmt.Println("defer 1")
    defer fmt.Println("defer 2")
    defer fmt.Println("defer 3")

    fmt.Println("main function running")
}

Output

main function running defer 3 defer 2 defer 1

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Common Pitfalls

One common mistake is expecting deferred functions to run in the order they appear. They actually run in reverse order (LIFO). Another pitfall is deferring functions that capture variables which may change before the defer runs.

Always remember that deferred calls execute after the surrounding function returns, so variable values might differ if not captured properly.

package main

import "fmt"

func main() {
    for i := 0; i < 3; i++ {
        defer fmt.Println(i) // This prints 2, 1, 0 because defer captures i by value at call time
    }
}

Output

2 1 0

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Quick Reference

Concept	Description
defer	Delays execution of a function until surrounding function returns
Multiple defers	Allowed; execute in last-in, first-out order
Variable capture	Deferred functions capture variables at defer statement execution
Use cases	Resource cleanup, closing files, unlocking mutexes

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Key Takeaways

Multiple defer statements run in reverse order of their appearance (LIFO).

Deferred functions execute after the surrounding function returns.

Be careful with variable values captured by deferred functions inside loops.

Use defer to simplify cleanup tasks like closing files or releasing locks.