Tell me more about WaitGroup: what is it used for, and what methods does it have?

WaitGroup in Go is used to wait for a group of goroutines to finish. It provides a convenient way to synchronize parallel tasks.

Main methods:

• Add(int): increases or decreases the counter of goroutines to wait for.
• Done(): decreases the counter by 1, called when a goroutine finishes.
• Wait(): blocks execution until the counter reaches 0.

Example usage:

var wg sync.WaitGroup
wg.Add(2) // expecting 2 goroutines

go func() {
    defer wg.Done()
    // work 1
}()

go func() {
    defer wg.Done()
    // work 2
}()

wg.Wait() // wait for both to finish

This allows the main goroutine to wait for all launched parallel tasks to complete.