Limit the maximum number of Goroutine and Using channel communication Demo

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package main  
  
import (  
 "fmt"  
 "strconv"  
 "sync"  
 "time"  
)  
  
// Maximum goroutine  
const goSize = 5  
  
// Producer Producer  
type Producer struct {  
 Item string  
}  
  
// Result result struct  
type Result struct {  
 Code   int  
 Stdout string  
}  
  
// RunJob job  
func RunJob(item string) (result Result) {  
 result.Code = 200  
 result.Stdout = item  
 return  
}  
  
// RoutineRun  go routine run job  
func RoutineRun(wg *sync.WaitGroup, producers chan Producer, result chan Result) {  
 for i := 0; i < goSize; i++ {  
  wg.Add(1)  
  go func() {  
   defer wg.Done()  
   for producer := range producers {  
    time.Sleep(time.Second)  
    ret := RunJob(producer.Item)  
    result <- ret  
   }  
  }()  
 }  
}  
  
func main() {  
 var job Producer  
 wg := &sync.WaitGroup{}  
 jobCount := 20  
 // chan size cannot be smaller than jobCount  
 jobsChan := make(chan Producer, 100)  
 resultChan := make(chan Result, 100)  
  
 for i := 0; i < jobCount; i++ {  
  job.Item = "item: " + strconv.Itoa(i)  
  jobsChan <- job  
 }  
 close(jobsChan)  
  
 RoutineRun(wg, jobsChan, resultChan)  
 wg.Wait()  
 close(resultChan)  
  
 for {  
  ret, ok := <-resultChan  
  if !ok {  
   break  
  }  
  fmt.Println("code: ", ret.Code, "stdout", ret.Stdout)  
 }  
}