Is it possible to set a limit on the number of concurrently running threads in the Go language?

In Go, there is no built-in mechanism to directly limit the number of goroutines running simultaneously. Goroutines can be very numerous and lightweight. To limit the number of concurrently executing goroutines, semaphores or channels with limited capacity are usually used.

Example of limiting the number of goroutines using a channel:

package main

import (
    "fmt"
    "sync"
    "time"
)

func worker(id int, sem chan struct{}, wg *sync.WaitGroup) {
    defer wg.Done()
    sem <- struct{}{} // acquire a slot
    fmt.Printf("Worker %d started\n", id)
    time.Sleep(time.Second) // work
    fmt.Printf("Worker %d finished\n", id)
    <-sem // release the slot
}

func main() {
    const maxConcurrent = 3
    sem := make(chan struct{}, maxConcurrent) // limit channel
    var wg sync.WaitGroup

    for i := 1; i <= 10; i++ {
        wg.Add(1)
        go worker(i, sem, &wg)
    }

    wg.Wait()
}

Here, the channel sem with buffer maxConcurrent limits the number of goroutines running simultaneously to 3.