如何为包含DB conn之类的应用程序包设置全局配置？

Question

I've structured my application in two packages so far - main and app

In my main() I start my server:

func main() {
    router := app.CreateRouter(app.Routes())
    log.Fatal(http.ListenAndServe(":8080", router))
}

In app, I have a Config struct which has a method connectToDB:

type Config struct {
    DB *sql.DB
}

func (c *Config) connectToDB() {
    connectionString := fmt.Sprintf("user=%s password=%s dbname=%s sslmode=disable", os.Getenv("DB_USERNAME"), os.Getenv("DB_PASSWORD"), os.Getenv("DB_NAME"))
    var err error
    c.DB, err = sql.Open("postgres", connectionString)
    if err != nil {
        log.Fatal(err)
    }
}

func init() {
    c := Config{}
    c.connectToDB()
}

However, I have various handlers and if I want to make use of Config.DB, how can I do that?

For example, in app.UserIndex, how can I get to Config.DB?

func UserIndex(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
    fmt.Fprint(w, "test!
")
}

Now, one thing I can do is set a global variable, such as

var c Config

Then, I can access c.DB anywhere in package app. However, this feels bad..

Answer 1

You can make an App variable to keep there config and some other useful settings for it eg Http time-out

var (
      App struct {
           DB         *sql.DB
           Timeout time.Duration
           ...
      }
)

Then make methods on this structure. This way config will be incapsulated in application instance.