This is an example of using a buffered channel to limit the number of goroutines running at the same time. It will start a server locally listening port 9988, so if there is a warning from firewall on windows, allow it. This, I think, is very useful when scraping the Internet if you want to limit the concurrent connections.

limitGoroutines.go

package main

import (
	"fmt"
	"html"
	"io/ioutil"
	"log"
	"net/http"
	"sync"
	"time"
)

func GetConcurrently() {
	// set limit to 10, and make a buffered channel
	limit := 10
	limiterChan := make(chan struct{}, limit)
	for i := 0; i < limit; i++ {
		limiterChan <- struct{}{}
	}

	// set num of goroutines to 1 << 6
	// num = 1 * 2^6 = 64
	num := 1 << 6

	// use sync.Waitgroup for managing goroutines
	wg := sync.WaitGroup{}
	wg.Add(num)
	log.Println(num, "routines will be started")

	for i := 0; i < num; i++ {
		go func(i int, wg *sync.WaitGroup) {
			t := time.Now()
			log.Println("goroutine", i, "is waiting for signal from channel")
			<-limiterChan
			log.Println("After", time.Now().Sub(t), "goroutine", i, "got the signal")

			// make a http GET request
			resp, _ := http.Get(fmt.Sprint("http://localhost:9988/", i))
			defer resp.Body.Close()
			byteResp, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				log.Println(err)
			}
			log.Println("goroutine", i, "received", string(byteResp))
			// give the signal back to the channel
			limiterChan <- struct{}{}
			wg.Done()
		}(i, &wg)
	}
	wg.Wait()
}

func handleGet(w http.ResponseWriter, r *http.Request) {
	_, err := fmt.Fprintf(w, "Hello, %q", html.EscapeString(r.URL.Path))
	if err != nil {
		log.Println(err)
	}
}

func main() {
	http.HandleFunc("/", handleGet)
	go GetConcurrently()
	log.Fatal(http.ListenAndServe(":9988", nil))
}

When limit = 2, num = 6:

2019/09/22 07:30:13 6 routines will be started
2019/09/22 07:30:13 goroutine 0 is waiting for signal from channel
2019/09/22 07:30:13 After 0s goroutine 0 got the signal
2019/09/22 07:30:13 goroutine 2 is waiting for signal from channel
2019/09/22 07:30:13 After 0s goroutine 2 got the signal
2019/09/22 07:30:13 goroutine 5 is waiting for signal from channel
2019/09/22 07:30:13 goroutine 3 is waiting for signal from channel
2019/09/22 07:30:13 goroutine 4 is waiting for signal from channel
2019/09/22 07:30:13 goroutine 1 is waiting for signal from channel
2019/09/22 07:30:13 goroutine 0 received Hello, "/0"
2019/09/22 07:30:13 After 13.0035ms goroutine 5 got the signal
2019/09/22 07:30:13 goroutine 2 received Hello, "/2"
2019/09/22 07:30:13 After 13.0035ms goroutine 3 got the signal
2019/09/22 07:30:13 goroutine 5 received Hello, "/5"
2019/09/22 07:30:13 After 14.0013ms goroutine 4 got the signal
2019/09/22 07:30:13 goroutine 3 received Hello, "/3"
2019/09/22 07:30:13 After 14.0013ms goroutine 1 got the signal
2019/09/22 07:30:13 goroutine 4 received Hello, "/4"
2019/09/22 07:30:13 goroutine 1 received Hello, "/1"