Concurrency in Go – Goroutines and Sync.WaitGroup Tutorial

What is a Goroutine?

A goroutine is a lightweight thread managed by the Go runtime, letting functions run concurrently with very low overhead.

func sayHello() {
    fmt.Println("Hello from goroutine")
}

go sayHello() // runs concurrently

Waiting for Goroutines with sync.WaitGroup

Since the main function doesn't wait for goroutines by default, sync.WaitGroup is used to block until a group of goroutines finishes.

var wg sync.WaitGroup

for i := 1; i <= 3; i++ {
    wg.Add(1)
    go func(id int) {
        defer wg.Done()
        fmt.Println("Worker", id, "done")
    }(i)
}

wg.Wait() // blocks until all goroutines call Done()

Why Goroutines Matter

Goroutines make it easy to write highly concurrent programs — handling thousands of simultaneous tasks with far less memory overhead than traditional OS threads.