总是有 x 个 goroutine 在任何时候运行

谢谢大家帮我解决这个问题.然而，我觉得没有人真的提供了既有效又简单易懂的东西，尽管你们都帮助我理解了这项技术.

我最后所做的是，我认为作为我的具体问题的答案，我更容易理解和实际，所以我会把它贴在这里，以防其他人有同样的问题.

不知何故，这最终看起来很像OneofOne发布的内容，这很棒，因为现在我明白了.但是OneofOne的代码一开始我发现很难理解，因为要将函数传递给函数，这让我很难理解位是用来做什么的.我认为这样做更有意义:

package main

import (
"fmt"
"sync"
)

const xthreads = 5 // Total number of threads to use, excluding the main() thread

func doSomething(a int) {
    fmt.Println("My job is",a)
    return
}

func main() {
    var ch = make(chan int, 50) // This number 50 can be anything as long as it's larger than xthreads
    var wg sync.WaitGroup

    // This starts xthreads number of goroutines that wait for something to do
    wg.Add(xthreads)
    for i:=0; i<xthreads; i++ {
        go func() {
            for {
                a, ok := <-ch
                if !ok { // if there is nothing to do and the channel has been closed then end the goroutine
                    wg.Done()
                    return
                }
                doSomething(a) // do the thing
            }
        }()
    }

    // Now the jobs can be added to the channel, which is used as a queue
    for i:=0; i<50; i++ {
        ch <- i // add i to the queue
    }

    close(ch) // This tells the goroutines there's nothing else to do
    wg.Wait() // Wait for the threads to finish
}