share a variable between some goroutines

main.go

package main

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

const (
  WORKER_LIMIT = 10
)

var Target []int = []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30}

type visited struct {
  mu   sync.Mutex
  mark map[int]bool
}

func (v *visited) Visit(visit int) {
  v.mu.Lock()
  v.mark[visit] = true
  v.mu.Unlock()
}

func (v *visited) Seen(target int) (seen bool) {
  v.mu.Lock()
  seen = v.mark[target]
  v.mu.Unlock()
  return
}

func worker() <-chan int {
  var wg sync.WaitGroup
  receiver := make(chan int)
  visited := visited{mark: make(map[int]bool)}

  go func() {
    defer close(receiver)

    for i := 0; i < WORKER_LIMIT; i++ {
      wg.Add(1)

      go func(no int) {
        defer wg.Done()

        for _, target := range Target {
          if visited.Seen(target) {
            continue
          }
          visited.Visit(target)
          fmt.Printf("no %2d: %2d\n", no, target)
          time.Sleep(time.Duration(rand.Intn(1e3)) * time.Millisecond)
        }
      }(i)
    }
    wg.Wait()
  }()

  return receiver
}

func main() {
  receiver := worker()
  for {
    _, ok := <-receiver
    if !ok {
      fmt.Println("finish")
      return
    }
  }
}

output.txt

$ go run main.go
no  0:  1
no  1:  2
no  2:  3
no  3:  4
no  4:  5
no  5:  6
no  6:  7
no  7:  8
no  8:  9
no  9: 10
no  7: 11
no  4: 12
no  8: 13
no  4: 14
no  3: 15
no  9: 16
no  4: 17
no  0: 18
no  2: 19
no  1: 20
no  4: 21
no  9: 22
no  8: 23
no  1: 24
no  2: 25
no  2: 26
no  7: 27
no  6: 28
no  0: 29
no  5: 30
finish