// *** in version 6.0: ***
import Synchronization

//Mutex owns the value it protects
let total = Mutex<Int>(0)

//Atomic changes a value without a lock
let hits = Atomic<Int>(0)

await withTaskGroup(of: Void.self) { group in
    for i in 1...100 {
        group.addTask {
            total.withLock { $0 += i }
            hits.wrappingAdd(1,
                ordering: .relaxed)
        }
    }
}

let sum = total.withLock { $0 }
//sum is 5050

let count = hits.load(ordering: .relaxed)
//count is 100

print("sum is \(sum)")
print("count is \(count)")