Goroutine-3of3-WaitGroups.go

package main

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

var program_start_time time.Time
var program_end_time time.Time
var total_completed_jobs = 0
var total_worker_busyness = 0

func init() {
  rand.Seed(time.Now().UnixNano())
}

func main() {
  program_start_time = time.Now()
  fmt.Println("----------------------------------------------------")
  var wg sync.WaitGroup
  wg.Add(4) // 4 = once for each goroutine
  go do_some_work("A", &wg)
  go do_some_work("B", &wg)
  go do_some_work("C", &wg)
  go do_some_work("D", &wg)
  wg.Wait()
  fmt.Println("----------------------------------------------------")
  program_end_time = time.Now()
  produce_final_report()
}

func do_some_work(work_id string, wg *sync.WaitGroup) {
  const NUM_OF_JOBS = 5
  for job_id := 1; job_id <= NUM_OF_JOBS; job_id++ {
    wait_ms := random_wait()
    fmt.Printf("job%d of work%s took:     %d ms\n", job_id, work_id, wait_ms)
    total_completed_jobs++
    total_worker_busyness += wait_ms
  }
  wg.Done()
}

func random_wait() int {
  const MIN_WAIT_MS = 50
  const MAX_WAIT_MS = 350
  wait_milliseconds := MIN_WAIT_MS + rand.Intn(MAX_WAIT_MS-MIN_WAIT_MS)
  time.Sleep(time.Duration(wait_milliseconds) * time.Millisecond)
  return wait_milliseconds
}

func produce_final_report() {
  fmt.Println("         Program time: ", program_end_time.Sub(program_start_time))
  fmt.Println(" Total completed jobs: ", total_completed_jobs)
  fmt.Println("Total worker busyness: ", total_worker_busyness, "ms")
}

output_1

----------------------------------------------------
job1 of workB took:     63 ms
job1 of workC took:     82 ms
job1 of workD took:     94 ms
job1 of workA took:     223 ms
job2 of workB took:     235 ms
job2 of workA took:     88 ms
job2 of workD took:     253 ms
job3 of workA took:     67 ms
job2 of workC took:     329 ms
job4 of workA took:     57 ms
job3 of workD took:     113 ms
job3 of workC took:     101 ms
job3 of workB took:     240 ms
job5 of workA took:     117 ms
job4 of workD took:     244 ms
job4 of workC took:     247 ms
job4 of workB took:     250 ms
job5 of workB took:     140 ms
job5 of workD took:     310 ms
job5 of workC took:     272 ms
----------------------------------------------------
         Program time:  1.034071978s
 Total completed jobs:  20
Total worker busyness:  3525 ms

output_2

----------------------------------------------------
job1 of workB took:     55 ms
job1 of workD took:     199 ms
job1 of workA took:     306 ms
job1 of workC took:     312 ms
job2 of workB took:     308 ms
job2 of workA took:     79 ms
job2 of workD took:     348 ms
job3 of workB took:     215 ms
job4 of workB took:     50 ms
job2 of workC took:     323 ms
job3 of workA took:     300 ms
job5 of workB took:     85 ms
job4 of workA took:     112 ms
job3 of workD took:     296 ms
job3 of workC took:     239 ms
job5 of workA took:     118 ms
job4 of workD took:     89 ms
job4 of workC took:     223 ms
job5 of workD took:     165 ms
job5 of workC took:     195 ms
----------------------------------------------------
         Program time:  1.296523594s
 Total completed jobs:  20
Total worker busyness:  4017 ms