My answer for `The Tour of Go`

cbrt.go

package main

import "fmt"
import "math/cmplx"

func Cbrt(x complex128) complex128 {
	z := x / 4
	for i := 0; i < 10; i++ {
		z = z - (cmplx.Pow(z, 3) - x) / (3 * z * z)
	}
	return z
}

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

fibonacci.go

package main

import "fmt"

// fibonacci is a function that returns
// a function that returns an int.
func fibonacci() func() int {
	times := 0
	x,y := 0,1
	return func() int {
		if times == 0 {
			times++
			return 0
		}else if times == 1 {
			times++
			return 1
		}
		tmp := y
		y = x + y
		x = tmp
		return y
	}
}

func main() {
	f := fibonacci()
	for i := 0; i < 10; i++ {
		fmt.Println(f())
	}
}

maps.go

package main

import "strings"
import "tour/wc"

func WordCount(s string) map[string]int {
	m := map[string]int{}
	for _,word := range strings.Fields(s) {
		m[word] = m[word] + 1
	}
	return m
}

func main() {
	wc.Test(WordCount)
}

slices.go

package main

import "tour/pic"

func Pic(dx, dy int) [][]uint8 {
	p := make([][]uint8, dy)
	for i := range p {
		p[i] = make([]uint8, dx)
	}
	return p
}

func main() {
	pic.Show(Pic)
}

sqrt.go

package main

import (
	"fmt"
)

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

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