mutexes.go

package main

import (
  "fmt"
  "math/rand"
  "runtime"
  "sync"
  "sync/atomic"
  "time"
)

func main() {
  var state = make(map[int]int)

  var mutex = &sync.Mutex{}

  var ops int64 = 0

  for r := 0; r < 100; r++ {
    go func() {
      total := 0
      for {
        key := rand.Intn(5)
        mutex.Lock()
        total += state[key]
        mutex.Unlock()
        atomic.AddInt64(&ops, 1)

        runtime.Gosched()
      }
    }()
  }

  for w := 0; w < 10; w++ {
    go func() {
      key := rand.Intn(5)
      val := rand.Intn(100)
      mutex.Lock()
      state[key] = val
      mutex.Unlock()
      atomic.AddInt64(&ops, 1)
      runtime.Gosched()
    }()
  }

  time.Sleep(time.Second)

  opsFinal := atomic.LoadInt64(&ops)
  fmt.Println("ops:", opsFinal)

  mutex.Lock()
  fmt.Println("state:", state)
  mutex.Unlock()
}