simple.go

package main

import (
	"fmt"
	"os"
	"runtime"
	"runtime/pprof"
	"strconv"
	"time"
)

type Buffer struct {
}

func (buf *Buffer) Write(p []byte) (n int, err error) {
	len := len(p)
	return len, err
}

//go:noinline
func deepcall(n int) {
	if n > 0 {
		deepcall(n - 1)
	}
	time.Sleep(time.Second * 10)
}

func main() {
	max := 0
	if len(os.Args) > 1 {
		arg := os.Args[1]
		max, _ = strconv.Atoi(arg)
	}
	fmt.Printf("expected number of goroutine: %v\n", max+1)
	for i := 0; i < max; i++ {
		go deepcall(10)
	}
	fmt.Printf("got num of goroutine: %v\n", runtime.NumGoroutine())
	time.Sleep(time.Second)

	start := time.Now()
	var buf Buffer
	pprof.Lookup("goroutine").WriteTo(&buf, 0)
	elasped := time.Since(start)

	fmt.Printf("time cost: %v\n", elasped)
}