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// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package sql_test
import (
"context"
"database/sql"
"flag"
"log"
"os"
"os/signal"
"time"
)
var pool *sql.DB // Database connection pool.
func Example_openDBCLI() {
id := flag.Int64("id", 0, "person ID to find")
dsn := flag.String("dsn", os.Getenv("DSN"), "connection data source name")
flag.Parse()
if len(*dsn) == 0 {
log.Fatal("missing dsn flag")
}
if *id == 0 {
log.Fatal("missing person ID")
}
var err error
// Opening a driver typically will not attempt to connect to the database.
pool, err = sql.Open("driver-name", *dsn)
if err != nil {
// This will not be a connection error, but a DSN parse error or
// another initialization error.
log.Fatal("unable to use data source name", err)
}
defer pool.Close()
pool.SetConnMaxLifetime(0)
pool.SetMaxIdleConns(3)
pool.SetMaxOpenConns(3)
ctx, stop := context.WithCancel(context.Background())
defer stop()
appSignal := make(chan os.Signal, 3)
signal.Notify(appSignal, os.Interrupt)
go func() {
select {
case <-appSignal:
stop()
}
}()
Ping(ctx)
Query(ctx, *id)
}
// Ping the database to verify DSN provided by the user is valid and the
// server accessible. If the ping fails exit the program with an error.
func Ping(ctx context.Context) {
ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
defer cancel()
if err := pool.PingContext(ctx); err != nil {
log.Fatalf("unable to connect to database: %v", err)
}
}
// Query the database for the information requested and prints the results.
// If the query fails exit the program with an error.
func Query(ctx context.Context, id int64) {
ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
defer cancel()
var name string
err := pool.QueryRowContext(ctx, "select p.name from people as p where p.id = :id;", sql.Named("id", id)).Scan(&name)
if err != nil {
log.Fatal("unable to execute search query", err)
}
log.Println("name=", name)
}
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