Golang 마이크로서비스 개발로 어떤 핵심 비즈니스 기능을 달성할 수 있나요?

package main

import (
    "fmt"
    "log"
    "net/http"
)

func main() {
    http.HandleFunc("/hello", helloHandler)
    log.Fatal(http.ListenAndServe(":8080", nil))
}

func helloHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "Hello, World!")
}

package main

import (
    "database/sql"
    "fmt"
    "log"

    _ "github.com/go-sql-driver/mysql"
)

func main() {
    db, err := sql.Open("mysql", "user:password@tcp(localhost:3306)/database")
    if err != nil {
        log.Fatal(err)
    }
    defer db.Close()

    rows, err := db.Query("SELECT * FROM users")
    if err != nil {
        log.Fatal(err)
    }
    defer rows.Close()

    for rows.Next() {
        var id int
        var name string
        err = rows.Scan(&id, &name)
        if err != nil {
            log.Fatal(err)
        }
        fmt.Println(id, name)
    }
}

package main

import (
    "log"

    "github.com/streadway/amqp"
)

func main() {
    conn, err := amqp.Dial("amqp://guest:guest@localhost:5672/")
    if err != nil {
        log.Fatal(err)
    }
    defer conn.Close()

    ch, err := conn.Channel()
    if err != nil {
        log.Fatal(err)
    }
    defer ch.Close()

    q, err := ch.QueueDeclare(
        "hello",
        false,
        false,
        false,
        false,
        nil,
    )
    if err != nil {
        log.Fatal(err)
    }

    err = ch.Publish(
        "",
        q.Name,
        false,
        false,
        amqp.Publishing{
            ContentType: "text/plain",
            Body:        []byte("Hello, RabbitMQ!"),
        },
    )
    if err != nil {
        log.Fatal(err)
    }
}

package main

import (
    "fmt"
    "log"
    "net/http"

    "github.com/dgrijalva/jwt-go"
)

var jwtKey = []byte("secret_key")

type Claims struct {
    Username string `json:"username"`
    jwt.StandardClaims
}

func main() {
    http.HandleFunc("/login", loginHandler)
    http.HandleFunc("/protected", authMiddleware(protectedHandler))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

func loginHandler(w http.ResponseWriter, r *http.Request) {
    username := r.FormValue("username")
    password := r.FormValue("password")

    if username == "admin" && password == "admin" {
        token := jwt.NewWithClaims(jwt.SigningMethodHS256, Claims{
            Username: username,
        })

        tokenString, err := token.SignedString(jwtKey)
        if err != nil {
            log.Fatal(err)
        }

        fmt.Fprintln(w, tokenString)
    } else {
        w.WriteHeader(http.StatusUnauthorized)
        fmt.Fprintln(w, "Username or password incorrect")
    }
}

func protectedHandler(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintln(w, "Protected resource")
}

func authMiddleware(next http.HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        tokenString := r.Header.Get("Authorization")
        token, err := jwt.ParseWithClaims(tokenString, &Claims{}, func(token *jwt.Token) (interface{}, error) {
            return jwtKey, nil
        })

        if claims, ok := token.Claims.(*Claims); ok && token.Valid {
            fmt.Println(claims.Username)
            next(w, r)
        } else {
            w.WriteHeader(http.StatusUnauthorized)
            fmt.Fprintln(w, "Unauthorized")
        }
    }
}