Sqrt by Newton's method https://en.wikipedia.org/wiki/Newton%27s_method

sqrt.go

package main

import (
	"fmt"
	"math"
)

func Sqrt(x float64) float64 {
	z := x / 2
	epsilon := 0.001
	for {
		delta := (z*z - x) / (2*z)
		fmt.Println(delta)
		z -= delta
		if math.Abs(delta) < epsilon {
			break
		}
	}
	return z
}

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