Module 3: Go’s Unique Features

Last modified: 18 December 2024

Detailed Topics:

Pointers and Memory

Go’s pointers allow you to work with memory addresses directly, but they differ significantly from C++ pointers. In Go:

  • There is no pointer arithmetic, making them safer to use.

  • Variables and pointers are garbage collected, reducing the risk of memory leaks.

Example 1:

package main
import "fmt"

func main() {
    x := 42
    p := &x // Pointer to x
    fmt.Println(*p) // Dereference pointer to get value

    *p = 21 // Modify value through the pointer
    fmt.Println(x) // Prints 21
}

Concurrency

Concurrency is a core feature of Go, achieved through goroutines and channels. Goroutines are lightweight threads, while channels facilitate safe communication between them. The select statement allows you to wait on multiple channel operations.

Example 2:

package main
import (
    "fmt"
    "time"
)

func worker(id int, ch chan string) {
    for msg := range ch {
        fmt.Printf("Worker %d received: %s\n", id, msg)
    }
}

func main() {
    ch := make(chan string)
    go worker(1, ch)
    go worker(2, ch)

    for i := 0; i < 5; i++ {
        ch <- fmt.Sprintf("Task %d", i)
    }
    close(ch)
    time.Sleep(time.Second) // Ensure workers finish
}

Error Handling

Go emphasizes explicit error handling using error values. Functions often return errors as their last return value, enabling straightforward checking.

Example 3:

package main
import (
    "fmt"
    "os"
)

func readFile(filename string) error {
    file, err := os.Open(filename)
    if err != nil {
        return fmt.Errorf("failed to open file: %w", err)
    }
    defer file.Close()

    buf := make([]byte, 1024)
    _, err = file.Read(buf)
    if err != nil {
        return fmt.Errorf("failed to read file: %w", err)
    }
    fmt.Println(string(buf))
    return nil
}

func main() {
    err := readFile("example.txt")
    if err != nil {
        fmt.Println("Error:", err)
    }
}

Detailed Hands-On:

1. Create a Multi-Threaded Counter Using Goroutines

Goal: Use goroutines and channels to safely increment a shared counter.

Example 4:

package main
import (
    "fmt"
    "sync"
)

func main() {
    counter := 0
    var mu sync.Mutex
    var wg sync.WaitGroup

    for i := 0; i < 10; i++ {
        wg.Add(1)
        go func() {
            mu.Lock()
            counter++
            mu.Unlock()
            wg.Done()
        }()
    }

    wg.Wait()
    fmt.Println("Final Counter:", counter)
}

2. Synchronize with Buffered and Unbuffered Channels

Goal: Use buffered and unbuffered channels to coordinate goroutines.

Example 5:

package main
import "fmt"

func producer(ch chan int) {
    for i := 0; i < 5; i++ {
        ch <- i
        fmt.Println("Produced:", i)
    }
    close(ch)
}

func consumer(ch chan int) {
    for item := range ch {
        fmt.Println("Consumed:", item)
    }
}

func main() {
    ch := make(chan int, 2) // Buffered channel
    go producer(ch)
    consumer(ch)
}

3. Write Error-Handling Functions for File Operations

Goal: Implement idiomatic error handling in file operations.

Example 6:

package main
import (
    "fmt"
    "os"
)

func writeFile(filename string, content string) error {
    file, err := os.Create(filename)
    if err != nil {
        return fmt.Errorf("could not create file: %w", err)
    }
    defer file.Close()

    _, err = file.WriteString(content)
    if err != nil {
        return fmt.Errorf("could not write to file: %w", err)
    }
    return nil
}

func main() {
    err := writeFile("output.txt", "Hello, Go!")
    if err != nil {
        fmt.Println("Error:", err)
    } else {
        fmt.Println("File written successfully!")
    }
}