What is defer? How does it work? Is it called during a panic?

In Go, the keyword defer is used to call a function at a later time — it will be executed after the surrounding function finishes, regardless of how it ends (normally or with an error).

How defer works:

• When the defer statement is executed, the function is not called immediately but is placed on a stack of deferred calls.
• After the function in which defer was declared finishes, all deferred functions are called in reverse order.

During a panic, deferred functions are still called, which allows, for example, to properly release resources or log errors before the program terminates.

Example:

func example() {
    defer fmt.Println("Deferred call")
    fmt.Println("Before panic")
    panic("Something went wrong")
    // The deferred call will execute even after a panic
}

In this example, "Deferred call" will be printed despite the panic.