import Foundation let group1 = DispatchGroup() func a(_ name: String) { print("Good night, \(name)..") sleep(2) print("Morning, \(name)!") group1.leave() } group1.enter() DispatchQueue.global().async { a("Anna") } group1.enter() DispatchQueue.global().async { a("Bob") } group1.enter() DispatchQueue.global().async { a("Cony") } group1.notify(queue: .main) { print("*** Good morning, all! ***") }