How can you efficiently launch and manage a large number of goroutines, for example, around 100,000?

For effectively launching and managing around 100,000 goroutines in Go, it is important to consider several aspects:

1. Using a worker pool — instead of launching all goroutines at once, create a fixed-size pool (for example, a few hundred), and distribute tasks among them. This reduces the load on the scheduler and decreases memory consumption.

2. Resource control — goroutines are lightweight, but each uses a stack (by default a few kilobytes), so it is important to avoid launching too many simultaneously without control.

3. Using channels for synchronization — to manage the lifecycle of goroutines and pass data between them.

4. Context (context.Context) — for cancellation and timeouts.

Example of a simple worker pool:

package main

import (
    "fmt"
    "sync"
)

func worker(id int, jobs <-chan int, results chan<- int, wg *sync.WaitGroup) {
    defer wg.Done()
    for j := range jobs {
        // Process task
        results <- j * 2
    }
}

func main() {
    const numJobs = 100000
    const numWorkers = 100

    jobs := make(chan int, numJobs)
    results := make(chan int, numJobs)

    var wg sync.WaitGroup

    for w := 1; w <= numWorkers; w++ {
        wg.Add(1)
        go worker(w, jobs, results, &wg)
    }

    for j := 1; j <= numJobs; j++ {
        jobs <- j
    }
    close(jobs)

    wg.Wait()
    close(results)

    // Process results
    count := 0
    for r := range results {
        _ = r // use the result
        count++
    }
    fmt.Println("Number of tasks processed:", count)
}

This approach allows efficient management of a large number of tasks using a limited number of goroutines.