My GoTour Exercise #44 (http://tour.golang.org/#44) solution

gistfile1.go

package main

import (
	"fmt"
	"math"
)

func sqrt(target, guess float64) float64 {
	return guess - (math.Pow(guess, 2)-target)/(2*guess)
}

func inequiv(a, b float64) bool {
	return math.Nextafter(a, b) != b
}

func Sqrt(x float64) float64 {
	curr, guess := 0.0, 10.0
	for inequiv(curr, guess) {
		curr = sqrt(x, guess)
		guess = (curr + guess) / 2
	}
	return guess
}

func main() {
	fmt.Println(Sqrt(2))
	fmt.Println(math.Sqrt(2))
}

tabs!