docs(example): code example (#51)

See the issue for details
- Documentations #15

example/main.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/rasatmaja/mura/v2"
+)
+
+// Config ...
+type Config struct {
+	Host string `env:"SERVER_HOST" default:"localhost"`
+	Port int    `env:"SERVER_PORT" default:"8080"`
+	TLS  bool   `env:"SERVER_TLS" default:"true"`
+}
+
+func main() {
+	cfg := new(Config)
+
+	err := mura.Unmarshal(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	print(cfg)
+}
+
+func print(i interface{}) {
+	s, _ := json.MarshalIndent(i, "", "\t")
+	fmt.Println("============== ENV ==============")
+	fmt.Printf("%s \n", s)
+	fmt.Println("=================================")
+}