Go - lesson 5 | HackIndia Skills

Go - lesson 5 | HackIndia Skills | HackIndia

Example

Small worker example

This example calculates a total in a goroutine and sends it back on a channel. It uses only the standard library.

A channel made with make(chan int) is unbuffered. The send waits until another goroutine receives the value.

package main

import "fmt"

type Order struct {
	ID     string
	Amount int
}

func totalAsync(orders []Order) <-chan int {
	result := make(chan int)

	go func() {
		total := 0
		for _, order := range orders {
			total += order.Amount
		}
		result <- total
	}()

	return result
}

func main() {
	orders := []Order{
		{ID: "upi-101", Amount: 199},
		{ID: "upi-102", Amount: 249},
	}

	totalCh := totalAsync(orders)
	fmt.Println("doing other work")

	total := <-totalCh
	fmt.Println("total rupees:", total)
}

Example

Buffered channel option

A channel made with make(chan string, 1) has space for one value. The sender can place one value without waiting for the receiver immediately.

This is useful for small one-shot signals, not for hiding slow code.

func sendReceiptAsync(orderID string) <-chan string {
	done := make(chan string, 1)

	go func() {
		// Replace this later with real email, SMS, or webhook code.
		done <- "receipt queued for " + orderID
	}()

	return done
}

Add goroutines and channels

One idea

Where it fits

Use the pattern

Small worker example

Use direction

Avoid goroutine leaks

Buffered channel option

Do this now

Quick check