my solution on A Tour of Go Exercise: Loops and Functions , http://tour.golang.org/#24

square-root-function-using-Newtons-method.go

package main

import (
  "fmt"
  "math"
)

func Sqrt(x float64) float64 {
  z := x
  n := 0.0
  
  for math.Abs(n-z) > 1e-10 {
    n, z = z, z - (z*z-x)/(2*z)
  }
  return z
}

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