How to Pass db to router functions

[ghost]

I'm opening the sqlite database in the main function

db, err := sql.Open("sqlite3", "./libreread.db")
CheckError(err)
defer db.Close()

And I have these router handlers

r.GET("/", GetHomePage)
r.GET("/signin", GetSignIn)
r.POST("/signin", PostSignIn)
...

How to pass that db value through the router handler func PostSignin(c *gin.Context) ?

So that I could avoid opening and closing the database each time in the functions.

Thanks!

[nazwa]

I usually create a middleware that sets a context value.

func Site(activeSite *sites.Site) gin.HandlerFunc {
	return func(c *gin.Context) {

		c.Set(constants.CONTEXT_SITE, activeSite)
		c.Next()
	}
}

	r.Use(middleware.Site(site))

And then inside your handler:

	site := c.MustGet(constants.CONTEXT_SITE).(*sites.Site)

Same concept applies to database objects :)

[easonlin404]

@mysticmode you can put db into a custom Env type:

type Env struct {
	db *sql.DB
}

func (e *Env) GetHomePage(c *gin.Context) {
	//e.db.Query("SELECT * FROM USER")
	//omitted..
}
func (e *Env) GetSignIn(c *gin.Context) {
	//omitted...
}

func (e *Env) PostSignIn(c *gin.Context) {
	//omitted...
}

func main() {
	db, _ := sql.Open("sqlite3", "./libreread.db")

	r := gin.New()

	env := &Env{db: db}
	r.GET("/", env.GetHomePage)
	r.GET("/signin", env.GetSignIn)
	r.POST("/signin", env.PostSignIn)
}

[McGiver-]

@mysticmode you can put db into a custom Env type:

type Env struct {
	db *sql.DB
}

func (e *Env) GetHomePage(c *gin.Context) {
	//e.db.Query("SELECT * FROM USER")
	//omitted..
}
func (e *Env) GetSignIn(c *gin.Context) {
	//omitted...
}

func (e *Env) PostSignIn(c *gin.Context) {
	//omitted...
}

func main() {
	db, _ := sql.Open("sqlite3", "./libreread.db")

	r := gin.New()

	env := &Env{db: db}
	r.GET("/", env.GetHomePage)
	r.GET("/signin", env.GetSignIn)
	r.POST("/signin", env.PostSignIn)
}

would this not effect performance since the environment receiver will be needed for every request which essentially makes it synchronous or at the very least is vulnerable to a data race?

[Demuzx]

Just open db connection as global concurrency variable and get access to it from any function, goroutine etc.

// DB is safe to be accessed from multiple goroutines
// https://golang.org/pkg/database/sql/#DB
var DBPointer, _ = sql.Open("sqlite3", "./libreread.db")

func DBTestHandler(c *gin.Context) {
	rows, err := DBPointer.Query("select * from Products")
	if err != nil {
		panic(err)
	}
	defer rows.Close()
}

func main() {
	r := gin.New()
	r.GET("/test", DBTestHandler)
	srv := &http.Server{
		Handler:      r,
		Addr:         "127.0.0.1:5050",
		WriteTimeout: 15 * time.Second,
		ReadTimeout:  15 * time.Second,
	}
	log.Fatal(srv.ListenAndServe())
}```

[nazwa]

@McGiver- No, this is totally fine. The database object is safe to use asynchronously. And also, you should treat the struct as a holder object only / something to group your endpoints in, and not as an active data source for operations within your handler functions if that makes any sense.