Functions, Returns & Defer

🐹 Go Language Lesson 9 Intermediate

Go functions are first-class citizens. They support multiple return values, named returns, and the defer keyword to manage resource cleanups.

1 Multiple Returns & The defer execution stack

Go functions provide two unique capabilities:

Multiple Return Values: Functions can return multiple values, commonly used to return a result alongside an `error` flag.
defer Keyword: Postpones the execution of a statement until the enclosing function completes. Deferred calls are pushed onto a Last-In-First-Out (LIFO) stack. This is highly useful for closing files or database streams, ensuring cleanup code runs even if exceptions occur.

2 Function Configurations Code

Let's run a program using multiple return functions and tracing deferred cleanup execution ordering:

Go — Multiple Returns & Defer ▶ Run Code

package main

import "fmt"

// Multiple return values
func divide(x, y int) (int, bool) {
    if y == 0 {
        return 0, false // division by zero is invalid
    }
    return x / y, true
}

func main() {
    // 1. Trace defer LIFO stack (execution order: 2, then 1)
    defer fmt.Println("Deferred print 1")
    defer fmt.Println("Deferred print 2")

    fmt.Println("Main function executing...")

    // 2. Multiple returns
    res, ok := divide(10, 2)
    if ok {
        fmt.Println("Result: ", res)
    } else {
        fmt.Println("Error occurred during division!")
    }
}

3 Code Challenge

Challenge: Write a function called `getStats` that accepts a slice of integers and returns both the sum (int) and count (int) of its elements. Test it in `main()` and print both values.