Cubic Root exercise for Go lang tour

cubic_root_ex.go

package main

import (
  "fmt"
	"math/cmplx"
	)

func Cbrt(x complex128) complex128 {
    z := complex128(1)
    for i := 0; i < 100; i++ {
        z = z - ((cmplx.Pow(z, 3) - x) / (3 * z * z))
    }
    return z
}

func main() {
    fmt.Println(Cbrt(8))
}