[Golang] 以 Mobile App 工程師視角，帶你進入 Golang 的世界 (Introduction of GoLang)

Introduction of GoLang
Johnny Sung
圖片來源：https://www.gctel.com/gopher-bounty-match-program/

Full stack developer
Johnny Sung (宋岡諺)
https://fb.com/j796160836
https://blog.jks.co
ff
ee/
https://www.slideshare.net/j796160836
https://github.com/j796160836

https://www.facebook.com/ProgrammersCreateLife/photos/a.962151813833697/5879918952056934/

App ⼯程師都做些什麼？
•拉 UI 畫⾯ (Zeplin, Figma)
•接 API (Swagger)
•⼿機特殊功能（例如：藍芽、相機...）
•修 Bug

接 API
•Swagger
•API Testing

Go 語⾔介紹
Golang 是 2007 年由 Google 設計的，2009 年對外公開
主要⽬的是簡化軟體開發並提⾼效率。
它在設計上強調簡單性、易讀性和⾼性能，
特別適合編寫低延遲的後端服務和分佈式系統。

Why Go ?
•強型別 (strongly typed)
•靜態型別 (statically typed)
•垃圾回收 (garbage collection)
•平⾏運算、並⾏性
•體積⼩、效能快、多平台

[Golang] 以 Mobile App 工程師視角，帶你進入 Golang 的世界 (Introduction of GoLang)

Why Go ?
https://www.docker.com/company/newsroom/media-resources/
https://kubernetes.io/
都是使⽤ Go 語⾔編寫的

GoLand by JetBrains IDE
https://www.jetbrains.com/go/

伺服器架構
•後端程式
•資料庫
•共享空間
•排程器 (Queue)

程式架構
•Data Model
•商業邏輯
•DB Interface, HTTP Interface

:=
短變數宣告
(Stort variable declaration)
變數建立 + 賦值 (assign) 的簡寫
package main
import "fmt"
func main() {
var a int = 3
b := 3
fmt.Println(a)
fmt.Println(b)
}

https://twitter.com/cachecoherent/status/1539867862227091456
指標(pointer)

指標 (pointer)
package main
import "fmt"
func main() {
var a int = 3
var p *int = &a
fmt.Println(a)
fmt.Println(&a)
fmt.Println(p)
fmt.Println(&p)
fmt.Println(*p)
}
// 3
// 0x14000124008
// 0x14000124008
// 0x14000126018
// 3
（印出值）
（印該變數記憶體位址）
（印出儲存的位址）
（印該變數記憶體位址）
（存取指標印出值）

Array（陣列） & Slice（切⽚）
•Array（陣列）：固定⻑度 (Fixed length) 的清單
•Slice（切⽚）：可以⾃由增加或減少⻑度的清單 (常⽤)

#include <stdio.h>
#include <stdlib.h>
int main() {
int *arr;
int i;
arr = malloc( 10 * sizeof(int) );
for (i = 0; i < 10; i++) {
arr[i] = i;
}
for (i = 0; i < 10; i++) {
printf("%d ", arr[i]);
}
free(arr);
return 0;
}
package main
import "fmt"
func main() {
var arr [10]int
for i := 0; i < 10; i++ {
arr[i] = i
}
for i := 0; i < 10; i++ {
fmt.Printf("%d ", arr[i])
}
}
Golang C
Array（陣列）

Slice（切⽚）
https://pjchender.dev/golang/slice-and-array/

for 搭配 range
package main
import "fmt"
func main() {
var arr = []int{46, 15, 73, 16, 66, 35}
for index, value := range arr {
fmt.Printf("%d ", index, value)
}
}

Class(類別)
•Go 語⾔沒有 class (類別) 只有 struct (結構)
type Car struct {
Brand string
Year int
}

type Car struct {
Brand string
Year int
}
func (p *Car) SetBrand(brand string) {
p.Brand = brand
}
func (p *Car) SetYear(year int) {
p.Year = year
}
func (p *Car) GetBrand() string {
return p.Brand
}
func (p *Car) GetYear() int {
return p.Year
}
public class Car {
private String brand;
private int year;
public Car(String brand, int year) {
this.brand = brand;
this.year = year;
}
public void setBrand(String brand) {
this.brand = brand;
}
public void setYear(int year) {
this.year = year;
}
public String getBrand() {
return brand;
}
public int getYear() {
return year;
}
}
Golang Java

接收器
讓 struct 有擴充 method 的可能
•值接收器 (value receiver)
•指標接收器 (point receiver)

接收器
•值接收器 (value receiver)
它會複製 struct 變數並傳進函式 (method)
func (c Car) GetName() int {
return c.Name
}

•指標接收器 (point receiver)
它會把 struct 轉成指標並傳進函式 (method) [常⽤]
接收器
p.Year = year
}

p.Year = year
}
(*p).Year = year
}
同義
⾃動解除參照（語法糖）
type Car struct {
Brand string
Year int
}

Error
package main
import (
"fmt"
"strconv"
)
func main() {
v = "s2"
s2, err := strconv.Atoi(v)
if err != nil {
fmt.Println(err) // strconv.Atoi: parsing "s2": invalid syntax
}
fmt.Printf("%T, %vn", s2, s2) // int, 0
}
Atoi (string to int)

Error
package main
import (
"fmt"
"strconv"
)
func main() {
v := "10"
s, err := strconv.Atoi(v)
if err != nil {
fmt.Println(err)
}
fmt.Printf("%T, %vn", s, s) // int, 10
}
Atoi (string to int)

defer（推遲、延後）
（⽰意簡化版範例）
package main
import (
"fmt"
"os"
)
func main() {
userFile := "my_file.txt"
fout, err := os.Create(userFile)
if err != nil {
fmt.Println(userFile, err)
return
}
defer fout.Close()
fout.WriteString("Hello, World.")
}

channel(通道)
package main
import "fmt"
func main() {
ch := make(chan int, 1)
defer close(ch)
ch <- 1
fmt.Print(<-ch)
}
var ch chan int
ch = make(chan int)
ch := make(chan int)
宣告塞值、取值
fatal error: all goroutines are asleep - deadlock!
緩衝區為 1
channel 型態

多執⾏緒 & WaitGroup
package main
import (
"fmt"
"sync"
)
func main() {
wg := sync.WaitGroup{}
wg.Add(2)
go func() {
defer wg.Done()
// Do something
}()
go func() {
defer wg.Done()
// Do something
}()
wg.Wait()
fmt.Println("Done")
}
package main
import (
"fmt"
"sync"
)
func main() {
wg.Add(2)
go worker(&wg)
go worker(&wg)
wg.Wait()
fmt.Println("Done")
}
func worker(wg *sync.WaitGroup) {
defer wg.Done()
// Do something
}

(async () => {
await Promise.all([
(async () => {
console.log('Worker 1 started');
await sleep(1000);
console.log('Worker 1 finished');
})(),
(async () => {
console.log('Worker 2 started');
await sleep(2000);
console.log('Worker 2 finished');
})(),
]);
console.log('Done');
})();
async function sleep(ms) {
return new Promise(resolve => setTimeout(() => resolve(), ms));
}
package main
import (
"fmt"
"sync"
"time"
)
func main() {
wg.Add(2)
go func() {
defer wg.Done()
fmt.Println("Worker 1 started")
time.Sleep(time.Millisecond * 1000)
fmt.Println("Worker 1 finished")
}()
go func() {
defer wg.Done()
fmt.Println("Worker 2 started")
fmt.Println("Worker 2 finished")
}()
wg.Wait()
fmt.Println("Done")
}
Golang JavaScript (NodeJS)

channel(通道)
package main
import "fmt"
func main() {
defer close(ch)
ch <- 1
fmt.Print(<-ch)
}
⚠
無緩衝區

https://decomyplace.com/n.php?id=9357
ch := make(chan int, 1)

https://www.dnaindia.com/business/report-what-s-cooking-on-the-cloud-2752364

https://static.wixstatic.com/media/160302bd324b4187b67b7f265c3b8f24.jpg/v1/
fi
ll/w_541,h_1333,al_c,q_85,enc_auto/160302bd324b4187b67b7f265c3b8f24.jpg
?
to
ch <- 1

⽤ range 讀取 channel
•⽤ range 讀取 channel 直到它被關閉
，若無值可取就會「等待」
•channel 關閉後，進⼊唯讀狀態
•for range 會讀完所有值才結束
// ... do something
for i := range ch {
fmt.Println(i)
}

https://blog.xuite.net/yafenyan/blog/60585613#

Fan out / Fan in
https://betterprogramming.pub/writing-better-code-with-go-concurrency-patterns-9bc5f9f73519

package main
import (
"fmt"
"sync"
"time"
)
func main() {
res := distributedSum(4, 1, 100)
fmt.Printf("Total: %dn", res)
}
Fan out / Fan in 範例

func distributedSum(numOfWorkers int, from int, to int) int {
wg := &sync.WaitGroup{}
wg.Add(numOfWorkers)
in := make(chan int, (to-from)-1)
out := make(chan int, numOfWorkers)
res := make(chan int, 1)
for i := 0; i < numOfWorkers; i++ {
go sumWorker(in, out, wg)
}
go compilationWorker(out, res)
for i := 0; i <= to; i++ {
in <- i // 塞資料給各個 sumWorkers
}
close(in) // 關閉資料窗⼝ (通知各個 sumWorkers 停⽌讀值)
wg.Wait() // 等待所有 workers 結束
close(out) // 關閉資料窗⼝ (通知 compilationWorker 停⽌讀值)
return <-res
}

func sumWorker(in chan int, out chan int, wg *sync.WaitGroup) {
defer wg.Done()
num := 0
for n := range in { // 讀取通道直到通道被關閉
num += n
}
fmt.Printf("partial sum: %dn", num)
out <- num
}
func compilationWorker(in chan int, out chan int) {
sum := 0
for i := range in { // 讀取通道直到通道被關閉
sum += i
}
out <- sum
}

•完全⾃學！Go 語⾔ (Golang) 實戰聖經
(The Go Workshop: Learn to write clean, efficient code and build high-performance applications with Go)
https://www.tenlong.com.tw/products/9789863126706
•下班加減學點 Golang 與 Docker
https://ithelp.ithome.com.tw/users/20104930/ironman/2647
•被選召的 Gopher 們，從零開始探索 Golang, Istio, K8s 數碼微服務世界
https://ithelp.ithome.com.tw/articles/10240228
•PJCHENder 未整理筆記
https://pjchender.dev/golang/go-getting-started/
參考資料

Mobile
API
CRUD
Login / Logout
Token (Session) JWT
/
Clean Architecture
Unit Test
Docker
Kubernetes (k8s)
Load Balancer
Database
Cache
Queue
Swagger
channel
mutex lock
CI / CD
MongoDB
RDBMS
MySQL
PostgreSQL
Memcached
Redis
RabbitMQ
grafana + prometheus
Pod
Service
Ingress
SOLID 5
OOP 3
goroutine
Backup
DRP (Disaster Recovery Plan)
Logs
BCP (Business Continuity Plan)
Git
Logger

obile
API
CRUD
Login / Logout
Token (Session) JWT
/
Clean Architecture
Unit Test
Docker
Kubernetes (k8s)
Swagger
channel
mutex lock
Pod
Service
Ingress
SOLID 5
OOP 3
goroutine

Mobile
Token (Session) JWT
Docker
Kubernetes (k8s)
Load Balancer
Database
Cache
Queue
Swagger
MongoDB
RDBMS
MySQL
PostgreSQL
Memcached
Redis
RabbitMQ
Pod
Service
Ingress
Logger

Mobile
CI / CD
grafana + prometheus
Backup
DRP (Disaster Recovery Plan)
Logs
BCP (Business Continuity Plan)
Git

[Golang] 以 Mobile App 工程師視角，帶你進入 Golang 的世界 (Introduction of GoLang)

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