# Start up

* Start up me-listen semua domain, port 9000 dan menghandle-nya dengan fungsi helloworld
* Untuk start up, kita menggunakan fungsi-fungsi pada [paket net/http](https://golang.org/pkg/net/http), yaitu http.HandlerFunc() dan http.ListenAndServe()

```go
package main

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

func main() {

    // handler
    handler := http.HandlerFunc(helloworld)

    // start server listening
    if err := http.ListenAndServe("0.0.0.0:9000", handler); err != nil {
        log.Fatalf("error: listening and serving: %s", err)
    }
}

// helloworld: basic http handler with response hello world string
func helloworld(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello World!")
}
```

* Kita juga bisa mendefinisikan parameter parameter untuk menjalankan server http melalui struct [http.Server](https://golang.org/pkg/net/http/#Server)

```go
package main

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

func main() {

    // parameter server
    server := http.Server{
        Addr:         "0.0.0.0:9000",
        Handler:      http.HandlerFunc(helloworld),
        ReadTimeout:  5 * time.Second,
        WriteTimeout: 5 * time.Second,
    }

    // mulai listening server
    if err := server.ListenAndServe(); err != nil {
        log.Fatalf("error: listening and serving: %s", err)
    }
}

// helloworld: basic http handler dengan response string hello world
func helloworld(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello World!")
}
```

* Listening server bisa dijalankan secara asynchronous melalui go routine. Dan untuk menangkap error yang terjadi digunakan channel.

```go
package main

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

func main() {

    // parameter server
    server := http.Server{
        Addr:         "0.0.0.0:9000",
        Handler:      http.HandlerFunc(helloworld),
        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()
    }()

    if err, ok := <-serverErrors; ok {
        log.Fatalf("error: listening and serving: %s", err)
    }
}

// helloworld: basic http handler dengan response string hello world
func helloworld(w http.ResponseWriter, r *http.Request) {
    fmt.Fprint(w, "Hello World!")
}
```