The database/sql package manages the connection pooling automatically for you.
sql.Open(..)
returns
a handle which represents a connection pool, not a single connection. The database/sql package automatically opens a new connection if all connections in the pool are busy.
Applied to your code this means, that you just need to share the db-handle and use it in the HTTP handlers:
package main
import (
"database/sql"
"fmt"
"github.com/gorilla/mux"
_ "github.com/go-sql-driver/mysql"
"log"
"net/http"
)
var db *sql.DB // global variable to share it between main and the HTTP handler
func main() {
fmt.Println("starting up")
var err error
db, err = sql.Open("mysql", "root@unix(/tmp/mysql.sock)/mydb") // this does not really open a new connection
if err != nil {
log.Fatalf("Error on initializing database connection: %s", err.Error())
}
db.SetMaxIdleConns(100)
err = db.Ping() // This DOES open a connection if necessary. This makes sure the database is accessible
if err != nil {
log.Fatalf("Error on opening database connection: %s", err.Error())
}
r := mux.NewRouter()
r.HandleFunc("/", HomeHandler)
http.Handle("/", r)
http.ListenAndServe(":8080", nil)
}
func HomeHandler(w http.ResponseWriter, r *http.Request) {
var msg string
err := db.QueryRow("SELECT msg FROM hello WHERE page=?", "home").Scan(&msg)
if err != nil {
fmt.Fprintf(w, "Database Error!")
} else {
fmt.Fprintf(w, msg)
}
}