# Fatal

* log.Fatal menyebabkan program berhenti setelah mencetak sebuah pesan error
* log.Fatal memanggil fungsi os.Exit(1) untuk memaksa program berhenti
* Penggunaan log.Fatal untuk menghentikan program sedini mungkin jika ada suatu kesalahan yang menyebabkan suatu kode selanjutnya tidak perlu dieksekusi sama sekali, atau kesalahan yang tidak dapat dipulihkan.
* log.Fatal biasanya hanya ada di dalam func init() atau func main()
* Dalam bab ini, kita akan memastikan bahwa log.Fatal hanya dipanggil di fungsi main, dan hanya dipanggil 1x. Hal ini dimaksudkan agar lebih mudah dalam mengelola kode dan memeriksa kesalahan-kesalahan fatal.
* Pindahkan semua kode main ke `func run() error{}`.
* Hapus seluruh call log.Fatal dan diganti dengan return error
* Panggil fungsi run() di main(), jika terjadi error eksekusi log.Fatal

```go
package main

import (
    "context"
    "essentials/controllers"
    "essentials/libraries/config"
    "essentials/libraries/database"
    "fmt"
    "log"
    "net/http"
    "os"
    "os/signal"
    "syscall"
    "time"

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

func main() {
    if _, ok := os.LookupEnv("APP_ENV"); !ok {
        config.Setup(".env")
    }

    if err := run(); err != nil {
        log.Printf("error: shutting down: %s", err)
        os.Exit(1)
    }
}

func run() error {
    // =========================================================================
    // App Starting

    log.Printf("main : Started")
    defer log.Println("main : Completed")

    // =========================================================================

    // Start Database

    db, err := database.Open()
    if err != nil {
        return fmt.Errorf("connecting to db: %v", err)
    }
    defer db.Close()

    // Create variable service with pattern dependency injection.
    // Inject koneksion db to type of Users
    service := controllers.Users{Db: db}

    // parameter server
    server := http.Server{
        Addr:         os.Getenv("APP_PORT"),
        Handler:      http.HandlerFunc(service.List),
        ReadTimeout:  5 * time.Second,
        WriteTimeout: 5 * time.Second,
    }

    serverErrors := make(chan error, 1)
    // mulai listening server
    go func() {
        log.Println("server listening on", server.Addr)
        serverErrors <- server.ListenAndServe()
    }()

    // Membuat channel untuk mendengarkan sinyal interupsi/terminate dari OS.
    // Menggunakan channel buffered karena paket signal membutuhkannya.
    shutdown := make(chan os.Signal, 1)
    signal.Notify(shutdown, os.Interrupt, syscall.SIGTERM)

    // Mengontrol penerimaan data dari channel,
    // jika ada error saat listenAndServe server maupun ada sinyal shutdown yang diterima
    select {
    case err := <-serverErrors:
        return fmt.Errorf("Starting server: %v", err)

    case <-shutdown:
        log.Println("caught signal, shutting down")

        // Jika ada shutdown, meminta tambahan waktu 5 detik untuk menyelesaikan proses yang sedang berjalan.
        const timeout = 5 * time.Second
        ctx, cancel := context.WithTimeout(context.Background(), timeout)
        defer cancel()

        if err := server.Shutdown(ctx); err != nil {
            log.Printf("main : Graceful shutdown did not complete in %v : %v", timeout, err)
            if err := server.Close(); err != nil {
                return fmt.Errorf("could not stop server gracefully: %v", err)
            }
        }
    }

    return nil
}
```

* File cmd/main.go berubah menjadi seperti berikut :

```go
package main

import (
    "essentials/libraries/config"
    "essentials/libraries/database"
    "essentials/schema"
    "flag"
    "fmt"
    "log"
    "os"

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

func main() {

    if _, ok := os.LookupEnv("APP_ENV"); !ok {
        config.Setup(".env")
    }

    if err := run(); err != nil {
        log.Printf("error: shutting down: %s", err)
        os.Exit(1)
    }
}

func run() error {

    // Start Database
    db, err := database.Open()
    if err != nil {
        return fmt.Errorf("connecting to db: %v", err)
    }
    defer db.Close()

    // Handle cli command
    flag.Parse()

    switch flag.Arg(0) {
    case "migrate":
        if err := schema.Migrate(db); err != nil {
            return fmt.Errorf("applying migrations: %v", err)
        }
        log.Println("Migrations complete")

    case "seed":
        if err := schema.Seed(db); err != nil {
            return fmt.Errorf("seeding database: %v", err)
        }
        log.Println("Seed data complete")
    }

    return nil
}
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://golang-microservices.rijalasepnugroho.com/build-rest-api-framework/fatal.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.