Now reading from the payload file

main.go

package main

import (
    "fmt"
    "math"
    "math/big"
    "github.com/iron-io/iron_go/worker"
)

func CalcNumerator(num int) int64 {
    odd := math.Mod(float64(num), 2)
    if (odd == 1) {
        return -1
    }
    return 1 // otherwise, it's even
}

type RangeToCalc struct {
    Begin int
    End int
}

func main() {
    sum := big.NewRat(0, 1)
	worker.ParseFlags()
	r := &RangeToCalc{}
	worker.PayloadFromJSON(r)

    for i := r.Begin; i <= r.End; i++ {
        leibnizNum := CalcNumerator(i)
        leibnizDen := int64(2 * i + 1)
        leibnizRat := big.NewRat(leibnizNum, leibnizDen)
        sum.Add(sum, leibnizRat)

        // fmt.Println("run number is: ", n)
        // fmt.Println("sum is: ", sum)
    }
    fmt.Println("Final sum is: ", sum)
}