AsyncTest

Test1

func execute(_ block: @escaping ()-> Void) {
  block()
}

print("A")
execute {
  print("B")
}
print("C")

Test2

func execute(_ block: @escaping ()-> Void) {
    DispatchQueue.global().async {
        block()
    }
}

print("A")
execute {
    print("B")
}
print("C")

Test3

func execute(_ block: @escaping ()-> Void) {
    DispatchQueue.global().async {
        block()
    }
    sleep(1)
}

print("A")
execute {
    print("B")
}
print("C")