You can have two wait groups one for y routines and another for (x-y) routines. For example : `

package main

import (
    "fmt"
    "sync"
)

//Implement fanin fanout pattern
//Scrape url for multiple urls in a list
//Code for 10 urls and 3 workers

func fanOut(results chan string, numOfWorkers int, urls []string, pwg *sync.WaitGroup) {
    urlChannel := make(chan string, len(urls))
    addUrlToChannel(urls, urlChannel)
    for i := 0; i < numOfWorkers; i++ {
        pwg.Add(1)
        go processWorker(pwg, urlChannel, results)
    }
    pwg.Wait()
    close(results)
}

func addUrlToChannel(urls []string, urlChannel chan string) {
    for _, url := range urls {
        urlChannel <- url
    }
    close(urlChannel)
}

func processWorker(pwg *sync.WaitGroup, urlChannel chan string, results chan string) {
    for url := range urlChannel {
        scrapeUrl(url, results)
    }
    pwg.Done()
}

func scrapeUrl(url string, results chan<- string) {
    results <- fmt.Sprintf("Successfully scraped %s: ", url)
}

func fanIn(scrapedUrls chan string, cwg *sync.WaitGroup) {
    defer cwg.Done()
    for url := range scrapedUrls {
        fmt.Println("Scraped url", url)
    }
}

func main() {
    urls := []string{
        "https://www.google.com",
        "https://www.github.com",
        "https://www.stackoverflow.com",
        "https://www.github.com",
        "https://www.stackoverflow.com",
        "https://www.google.com",
        "https://www.github.com",
        "https://www.stackoverflow.com",
        "https://www.google.com",
        "https://www.github.com",
    }
    results := make(chan string)
    var pwg sync.WaitGroup
    var cwg sync.WaitGroup
    numOfWorkers := 3
    //FanIn
    cwg.Add(1)
    go fanIn(results, &cwg)
    //FanOut
    fanOut(results, numOfWorkers, urls, &pwg)
    cwg.Wait()
    fmt.Println("Application ended")
}

`