Capstone: benchmark against real Redis

func runPhase(host string, port int, n, concurrency int, op string) result {
    perWorker := n / concurrency
    var latencies []time.Duration
    var mu sync.Mutex
    var wg sync.WaitGroup
    t0 := time.Now()
    for i := 0; i < concurrency; i++ {
        wg.Add(1)
        go func() { defer wg.Done(); worker(host, port, perWorker, op, &latencies, &mu) }()
    }
    wg.Wait()
    elapsed := time.Since(t0)
    sort.Slice(latencies, func(i, j int) bool { return latencies[i] < latencies[j] })
    return result{
        op: op, totalOps: len(latencies), elapsed: elapsed,
        throughput: float64(len(latencies)) / elapsed.Seconds(),
        p50:        latencies[len(latencies)/2],
        p99:        latencies[(len(latencies)*99)/100],
    }
}