type Config struct {
    Server struct {
        Host string `json:"host"`
        Port string `json:"port"`
        } `json:"server"`
    Postgres struct {
        Host     string `json:"host"`
        User     string `json:"user"`
        Password string `json:"password"`
        DB       string `json:"db"`
    } `json:"database"`
}

func main() {
    jsonConfig := []byte(`{
        "server":{
            "host":"localhost",
            "port":"8080"},
        "database":{
            "host":"localhost",
            "user":"db_user",
            "password":"supersecret",
            "db":"my_db"}}`)
    var config Config
    err := json.Unmarshal(jsonConfig, &config)
    if err != nil {
        panic(err)
    }
    fmt.Printf("Config: %+v\n", config)
}