Golang: how to verify number of processors on which a Go program is running

Question

I am new to Google Go (Golang). My question is related to this post What exactly does runtime.Gosched do?. The structure of code is as copied below. My question, is that when I change the number of processor in GOMAXPROCS, how do I verify how many processors it is running on. When I do 'top', it shows a.out process which consumes 100% or less resources even when GOMAXPROCS is more than 1. I would be grateful for your help.

package main

import (
    "fmt"
    "runtime"
    "sync"
)

var wg sync.WaitGroup

func doTasks() {
    fmt.Println(" Doing task ")
    for ji := 1; ji < 100000000; ji++ {
        for io := 1; io < 10; io++ {
            //Some computations
        }
    }
    runtime.Gosched()

    wg.Done()
}

func main() {
    wg.Add(1)
    runtime.GOMAXPROCS(1) // or 2 or 4
    go doTasks()
    doTasks()
    wg.Wait()
}

Answer 1

The largest number of logical CPUs the process can be running on at a given time is no more than the minimum of runtime.GOMAXPROCS(0) and runtime.NumCPU().

func MaxParallelism() int {
    maxProcs := runtime.GOMAXPROCS(0)
    numCPU := runtime.NumCPU()
    if maxProcs < numCPU {
        return maxProcs
    }
    return numCPU
}