simple worker example. https://play.golang.org/p/rAx_z-s0M-

worker_group.go

package main

import (
	"fmt"
	"sync"
)

func main() {
	workers := 3
	var wg sync.WaitGroup
	data := []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}

	for i, num := range data {
		wg.Add(1)
		go func(n int) {
			fmt.Println("number:", n)
			wg.Done()
		}(num)
		if i%workers == 0 {
			fmt.Println("worker done")
			wg.Wait()
		}

	}

	wg.Wait()
}