The problem is I get
about >1ms delay when I create one hundred/thousand gorountine.

func main() {
    for i := 0; i < 100; i++ { // or use 1000
        go func() { testWaitRoutine() }()
    }

    time.Sleep(10 * time.Second)
}

func testWaitRoutine() {
    channl := make(chan int, 1)

    go func() {
        channl <- time.Now().Nanosecond()
        time.Sleep(3 * time.Second)
        channl <- time.Now().Nanosecond()
    }()

    _, secondTime := <-channl, <-channl
    nowTime := time.Now().Nanosecond()
    delay := nowTime - secondTime
    println(delay)
}

OUTPUT show there are very few result count of microseconds and milliseconds delay, such as:

...
3000
338000
2000
...
1000
1000
72000
1000
...
2000
2000
1185000
1000
1000
...

Hardware: Both of MBP(2017) and Windows 10 have this phenomenon.

[Question]

Why will gorountine give a larger delay result sometimes than a stable delay number? What’s the underlay implementation causing?