Concurrent π calculation with Golang!

pi.go

package main

import (
	"fmt"
	"math"
	"runtime"
	"time"
)

// Using the Bailey–Borwein–Plouffe formula
func partialSum(ch chan<- float64, offset, workers, amount int) {
	var i, sum float64 = 0.0, 0.0
	for i = float64(offset); i < float64(offset+workers*amount); i += float64(workers) {
		sum += 1 / math.Pow(16, i) * (4/(8*i+1) - 2/(8*i+4) - 1/(8*i+5) - 1/(8*i+6))
	}
	ch <- sum
}

func main() {
	var (
		pi       = 0.0
		workers  = runtime.NumCPU()
		amount   = 1_0000_0000
		ch       = make(chan float64, workers)
		start    time.Time
		duration time.Duration
		i        int
	)

	defer close(ch)

	start = time.Now()
	for i = 0; i < workers; i++ {
		go partialSum(ch, i, workers, amount)
	}
	for i = 0; i < workers; i++ {
		pi += <-ch
	}
	duration = time.Since(start)

	fmt.Println("Calculated π:", pi)
	fmt.Println("Duration: ", duration)
	fmt.Println("Difference between math.Pi and calculated:", pi-math.Pi)
}