๐ฆ why Go?
I have been using Node for a long time. Node is best but not perfect. Go will be a good complement to Node's weaknesses. You can read this article to understand why I choose to Go.
package main
import (
"fmt"
"math"
)
func main() {
fmt.Printf("Hello %s", "๐น Go")
fmt.Println(math.Pi)
}package main
import "fmt"
func add(a int, b int) int {
return a + b
}
func subtract(a, b int) int {
return a - b
}
func swap(a, b int) (int, int) {
return b, a
}
// named return values
func split(number int) (a, b int) {
a = number / 10
b = number % 10
return
}
func main() {
fmt.Println(add(6,9)) // 15
fmt.Println(subtract(17, 10)) // 7
a, b := swap(10, 17)
fmt.Println(a, b) // 17 10
fmt.Println(split(19)) // 1 9
}package main
import "fmt"
// global variables
var canFly bool
var age int = 21
func main() {
// explict
var name string = "Cuong Duy Tran Nguyen"
// inferred
var job, address = "Software Engineer", "Ho Chi Minh city"
// shorthand
gender := "male"
// constant
const homeTown = "Tam Ky city, Quang Nam province"
fmt.Println(canFly, name, age, job, address, gender, homeTown)
}bool
string
int int8 int16 int32 int64
uint uint8 uint16 uint32 uint64 uintptr
byte // alias for uint8
rune // alias for int32
// represents a Unicode code point
float32 float64
complex64 complex128
package main
import "fmt"
func main() {
var (
name string = "Cuong Duy Nguyen"
age int = 21
)
fmt.Printf("type: %T, value: %v
", name, name)
fmt.Printf("type: %T, value: %v
", age, age)
}package main
import (
"fmt"
"math"
)
func main() {
var z uint = uint(math.Sqrt(64))
var i int = 7
var f float64 = float64(i)
fmt.Print(z, i, f)
}package main
import "fmt"
func main() {
for i := 0; i < 7; i++ {
fmt.Println(i)
}
// for continued
max := 0
for ; max < 7777 ; {
max += 7
}
fmt.Println(max)
// while
sum := 0
for sum < 777 {
sum += 7
}
fmt.Println(sum)
// forever
for {
fmt.Println("go")
}
}package main
import (
"fmt"
"runtime"
"time"
)
func compare(x, y int) (z string) {
if x > y {
z = "x is greater than y"
} else {
z = "x is smaller than y"
}
return
}
func isEven(number int) bool {
if num := number % 2; num == 0 {
return true
}
return false
}
// switch case
func checkOS() string {
switch os := runtime.GOOS; os {
case "linux":
return "๐ง Linux"
case "darwin":
return "๐ macOS"
default:
return os
}
}
// switch case without condition
func showGreeter() string {
h := time.Now().Hour()
switch {
case h < 12:
return "good morning"
case h < 17:
return "good afternoon"
default:
return "good evening"
}
}
func main() {
t := compare(6, 7)
fmt.Println(t)
fmt.Print(isEven(7))
fmt.Print(checkOS())
fmt.Println(showGreeter())
}A defer statement defers the execution of a function until the surrounding function returns.
Deferred function calls are pushed onto a stack. When a function returns, its deferred calls are executed in last-in-first-out order.
package main
import "fmt"
func main() {
fmt.Print("counting ")
for i := 0; i < 10; i++ {
defer fmt.Printf("%d ", i)
}
fmt.Print("done ")
// counting done 9 8 7 6 5 4 3 2 1 0
}package main
import "fmt"
func main() {
i, j := 10, 50
a := &i
fmt.Println(a, *a)
*a = 17
fmt.Println(a, *a, i)
var b *int = &j
fmt.Println(b, *b)
a = b
fmt.Println(*a, *b)
}package main
import "fmt"
type Point struct {
x int
y int
}
func main() {
// basic struct
p := Point{6, 9}
fmt.Println(p, p.x, p.y)
p.x = 1
p.y = 7
fmt.Println(p, p.x, p.y)
// struct with pointer
var a *Point = &p
fmt.Println(a, *a)
fmt.Println(a.x, (*a).x) // the same result
// init struct
var (
v1 = Point{1, 2} // has type Point
v2 = Point{x: 1} // Y:0 is implicit
v3 = Point{} // X:0 and Y:0
k = &Point{1, 2} // has type *Point
)
fmt.Println(v1, k, v2, v3)
}package main
import "fmt"
func main() {
var list [7]int
list[0] = 7
fmt.Println(list, list[1]) // [7 0 0 0 0 0 0] 0
oddNumbers := [3]int{3, 5}
oddNumbers[2] = 7
fmt.Println(oddNumbers) // [3 5 7]
var fullName [3]string = [3]string{"Cuong", "Duy", "Nguyen"}
fmt.Println(fullName) // [Cuong Duy Nguyen]
}package main
import "fmt"
func main() {
// 1. basic slice
a := []int{1, 2, 3, 5, 6, 7, 8, 9, 10}
a = a[:7]
fmt.Println(a) // [1 2 3 5 6 7 8]
// 2. slices are like references to arrays
pets := []string{"cat", "dog", "bird", "fish"}
fmt.Println(pets) // [cat dog bird fish]
list := pets[0:2]
fmt.Println(list) // [cat dog]
list[1] = "pig"
fmt.Println(list) // [cat pig]
fmt.Println(pets) // [cat pig bird fish]
// 3. slice length & capacity
// The capacity of a slice is the number of elements in the underlying array, counting from the first element in the slice.
s := []int{2, 3, 5, 7, 11, 13}
fmt.Printf("len=%d cap=%d %v
", len(s), cap(s), s)
// len=6 cap=6 [2 3 5 7 11 13]
// 4. slice the slice to give it zero length.
s = s[:1]
fmt.Printf("len=%d cap=%d %v
", len(s), cap(s), s)
// len=1 cap=6 [2]
// Extend its length.
s = s[:2]
fmt.Printf("len=%d cap=%d %v
", len(s), cap(s), s)
// len=2 cap=6 [2 3]
// Drop its first two values.
s = s[2:]
fmt.Printf("len=%d cap=%d %v
", len(s), cap(s), s)
// len=0 cap=4 []
s = s[:4]
fmt.Printf("len=%d cap=%d %v
", len(s), cap(s), s)
// len=4 cap=4 [5 7 11 13]
// 5. nil slices
// A nil slice has a length and capacity of 0 and has no underlying array.
var t []int
fmt.Println(t, len(t), cap(t)) // [] 0 0
if t == nil {
fmt.Println("nil!") // nil!
}
// 6. Creating a slice with make
x := make([]int, 10)
fmt.Printf("%d %d %v
", len(x), cap(x), x)
// 10 10 [0 0 0 0 0 0 0 0 0 0]
y := make([]int, 0, 5)
fmt.Printf("%d %d %v
", len(y), cap(y), y)
// 0 5 []
z := y[:5]
fmt.Printf("%d %d %v
", len(z), cap(z), z)
// 5 5 [0 0 0 0 0]
// 7. Appending to a slice
// cap will auto scale up depend on the added elements
m := []int{}
fmt.Printf("len=%d cap=%d %v
", len(m), cap(m), m)
// len=0 cap=0 []
m = append(m, 6, 5)
fmt.Printf("len=%d cap=%d %v
", len(m), cap(m), m)
// len=2 cap=2 [6 5]
m = append(m, 1, 2, 5, 6, 8, 9, 3)
fmt.Printf("len=%d cap=%d %v
", len(m), cap(m), m)
// len=9 cap=10 [6 5 1 2 5 6 8 9 3]
// 8. range
// contain i(index) & v(clone value)
var numbers []int = []int{1, 3, 7, 8}
for i, v := range numbers {
fmt.Println(i, v)
}
// 0 1
// 1 3
// 2 7
// 3 8
// skip the index or value by assigning to _
}package main
import "fmt"
type Point struct {
X, Y int
}
func main() {
// 1. Basic
var m map[string]Point = make(map[string]Point)
fmt.Printf("%v
", m) // map[]
m["L"] = Point{6, 9}
m["T"] = Point{0, 1}
fmt.Printf("%v %v
", m, m["T"]) // map[L:{6 9} T:{0 1}] {0 1}
// 2. Map literals
t := map[string]Point{
"foo": Point{3, 1},
"bar": Point {5, 6},
"taz": {10, 20}, // shorthand Struct
}
fmt.Printf("%v
", t)// map[bar:{5 6} foo:{3 1}]
// 3. Mutating maps
list := map[int]int {
1: 10,
2: 100,
3: 1000,
}
fmt.Printf("%v
", list) // map[1:10 2:100 3:1000]
// insert an element
list[4] = 10000
fmt.Printf("%v
", list) // map[1:10 2:100 3:1000 4:10000]
// delete an element
delete(list, 4)
fmt.Printf("%v
", list) // map[1:10 2:100 3:1000]
// test that a key is present
elem, ok := list[4]
fmt.Println(elem, ok) // 0 false
}package main
import "fmt"
func add(x int) func(int) int {
return func(y int) int {
return x + y
}
}
func main() {
value := add(3)(4)
fmt.Println(value) // 7
}package main
import (
"fmt"
"time"
)
type User struct {
name string
dob int
}
func (u User) age() int {
u.name = "๐"
return time.Now().Year() - u.dob
}
// Using pointer to modify struct's methods
func (u *User) changeName(name string) {
u.name = name
}
func main() {
user := User{"Cuong Duy Nguyen", 1998}
fmt.Println(user.age()) // 22
fmt.Println(user.name) // Cuong Duy Nguyen * not modify
user.changeName("Nguyแป
n Duy Cฦฐฦกng")
fmt.Println(user.name) // Nguyแป
n Duy Cฦฐฦกng * modify
}package main
import "fmt"
type Animal struct {
name, color string
}
func (animal Animal) Miaow() {
fmt.Printf("meow moew %s", animal.name)
}
type Cat interface {
Miaow()
}
func main() {
var cat Cat = Animal{"Dog", "black"}
cat.Miaow()
}package main
import "fmt"
func sum(c chan int, s []int) {
sum := 0
for _, v := range s {
sum += v
}
c <- sum
}
func main() {
s := []int{1, 5, 2, 8}
c := make(chan int, 5) // initialize number of channels.
go sum(c, s[:len(s) / 2])
go sum(c, s[len(s) / 2:])
x, y := <- c, <- c
fmt.Println(x, y, x + y) // 10 6 16
}-
๐ฆ golang.org
-
๐ฆ A Tour of Go
-
๐ณ Go Cheat Sheet
MIT ยฉ Cuong Nguyen