Defer: Delayed Execution in Go

Snippet

Defer: Delayed Execution in Go

The defer keyword schedules a function call to run immediately after the surrounding function returns. This is perfect for cleanup tasks like closing files or releasing resources. Deferred functions execute in Last-In-First-Out order, meaning the last defer added runs first when the function exits.

snippet.go
go
package main
import "fmt"
 
func main() {
	defer fmt.Println("World")
	fmt.Println("Hello")
}
 
func readFile(name string) {
	file := "open""
	defer fmt.Println("Closing:", file)
	fmt.Println("Reading:", name)
	file = "close"
}

Breakdown

defer fmt.Println("World")

Schedules fmt.Println to run after main() completes, but before it returns

fmt.Println("Hello")

Executes immediately, then deferred print runs after

defer fmt.Println("Closing:", file)

Captures current value of file variable for deferred execution

file = "close"

Variable changes, but deferred call already captured the original value

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Defer: Delayed Execution in Go

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