Newton's method Sqrt

package main

import (
    "fmt"
    "math"
)

func Sqrt(x float64) float64 {
    z := 1.0
    prevZ := z * 2
    i := 0

    for ; math.Abs(prevZ - z) > 0.00001; i++ {
        prevZ = z
        z -= (z*z - x) / (2*z)
    }

    fmt.Printf("i: %v\n", i)
    return z
}

func main() {
    fmt.Printf("Sqrt(8.5): %v\n", Sqrt(8.5))
    fmt.Printf("math.Sqrt(8.5): %v\n", math.Sqrt(8.5))
}