A Tour of Go: Exercise: Loops and Functions, https://go-tour-jp.appspot.com/flowcontrol/8

exercise_loops_and_functions.go

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z := 1.0
	for i := 0; i < 10; i++ {
		z = z - (math.Pow(z, 2)-x)/(2*z)
	}
	return z
}

func main() {
	for i := 1.0; i < 10; i++ {
		fmt.Printf("Sqrt(%f) = ", i)
		fmt.Println(
			math.Sqrt(i),
			Sqrt(i),
		)
	}
}