What is defer in Go?

Question

Accepted Answer

**defer** — schedules function call to run after surrounding function returns.

```go
func readFile(filename string) {
    file, err := os.Open(filename)
    if err != nil {
        log.Fatal(err)
    }
    defer file.Close()  // Will close when function returns

// Read file...
}
```

**Key points:**
- LIFO order (last in, first out).
- Arguments evaluated immediately.
- Runs even if function panics.

```go
func example() {
    defer fmt.Println("First")
    defer fmt.Println("Second")
    defer fmt.Println("Third")
    // Output: Third, Second, First
}
```

**Common uses:**
- Closing files.
- Unlocking mutexes.
- Closing database connections.
- Recovering from panics.

Go: What is defer in Go?