将查询移至处理程序将获得“未定义：db”（golang）

Question

I am trying to use Golang as a REST API. I have managed to get handlers to work and queries as well. But not got a query inside a handler to work.

When the query resides within the main() it works:

func handleRequests() {
    http.HandleFunc("/getuser", Getuser)
}

---> this handler gets respons on localhost:8080/getuser

func Getuser(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Getuser")
}

func main() {
    handleRequests()

    //Connect to db

    rows, err := db.Queryx(`SELECT "USER_ID","USER_NAME" FROM user`)
    for rows.Next() {
        results := make(map[string]interface{})
        err = rows.MapScan(results)
    fmt.Printf("%#v
", results)
    }

    log.Fatal(http.ListenAndServe(":8080", nil))
}

But when I move the query to the handler it gives an error that the db is not defined.

func handleRequests() {
    http.HandleFunc("/getuser", Getuser)
}

---> this gives the error that the db is not defined

func Getuser(w http.ResponseWriter, r *http.Request) {
    rows, err := db.Queryx(`SELECT "USER_ID","USER_NAME" FROM user`)
    for rows.Next() {
        results := make(map[string]interface{})
        err = rows.MapScan(results)
    fmt.Printf("%#v
", results)
    }
}

func main() {
    handleRequests()

    //Connect to db

    log.Fatal(http.ListenAndServe(":8080", nil))
 }

EDIT

Full code inside the handler (added db var as suggested), but gives various errors on "err".

 var db *sqlx.DB <---solved the db problem

 func Getsign(w http.ResponseWriter, r *http.Request) {
    rows, err := db.Queryx(`SELECT "USER_ID","USER_NAME" FROM user`)
    for rows.Next() {
        results := make(map[string]interface{})
        err = rows.MapScan(results)
        fmt.Printf("%#v
", results)
    }

    defer rows.Close()

    if err := rows.Err(); err != nil {
        log.Fatal(err)
    }
}

Any tip what I am doing wrong?

Answer 1

Define your db variable outside of main, e.g.:

var db *sql.DB

func handler(w http.ResponseWriter, r *http.Request) {
    rows, err := db.Query(...)
    // use it
}

func main() {
    db, _ = sql.Open(...)
}