What is the ’defer’ statement used for in Go? — Go Interview Question #13

The ‘defer‘ statement in Go is used to ensure that a function call, usually for cleaning up resources such as closing files or network connections, is executed later in the program just before the surrounding function returns. This helps developers manage resources effectively and avoid code duplication or potential errors.

Using ‘defer‘, you can schedule a function call and make sure it is executed regardless of how or where the surrounding function returns (either normally or via panic). The ‘defer‘ statement has the following general syntax:

defer functionName(arguments)

Consider the following example:

package main

import (
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("example.txt")
    if err != nil {
        fmt.Println("Error: ", err)
        return
    }
    defer file.Close()

    // Perform some operations on the file...
}

In this example, the ‘defer‘ statement schedules ‘file.Close()‘ to be called just before the ‘main‘ function returns. This ensures that the file is properly closed even if an error occurred or the function returned early.

In sum, the ‘defer‘ statement in Go allows you to manage resources efficiently, avoid code duplication, and handle potential errors effectively by scheduling a function call to be executed just before the surrounding function returns.