helloworld.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"os"

	"database/sql"

	_ "github.com/go-sql-driver/mysql"
)

func handler(w http.ResponseWriter, r *http.Request) {
	log.Print("Hello world received a request.")
	target := os.Getenv("TARGET")
	if target == "" {
		target = "World"
	}
	fmt.Fprintf(w, "Hello %s!\n", target)
}

// mustGetEnv is a helper function for getting environment variables.
// Displays a warning if the environment variable is not set.
func mustGetenv(k string) string {
	v := os.Getenv(k)
	if v == "" {
		log.Printf("Warning: %s environment variable not set.\n", k)
	}
	return v
}

func initSocketConnectionPool() (*sql.DB, error) {
	// [START cloud_sql_mysql_databasesql_create_socket]
	var (
		dbUser                 = mustGetenv("DB_USER")
		dbPwd                  = mustGetenv("DB_PASS")
		instanceConnectionName = mustGetenv("INSTANCE_CONNECTION_NAME")
		dbName                 = mustGetenv("DB_NAME")
	)

	var dbURI string
	dbURI = fmt.Sprintf("%s:%s@unix(/cloudsql/%s)/%s", dbUser, dbPwd, instanceConnectionName, dbName)

	// dbPool is the pool of database connections.
	dbPool, err := sql.Open("mysql", dbURI)
	if err != nil {
		return nil, fmt.Errorf("sql.Open: %v", err)
	}

	// [START_EXCLUDE]
	configureConnectionPool(dbPool)
	// [END_EXCLUDE]

	return dbPool, nil
	// [END cloud_sql_mysql_databasesql_create_socket]
}

// configureConnectionPool sets database connection pool properties.
// For more information, see https://golang.org/pkg/database/sql
func configureConnectionPool(dbPool *sql.DB) {
	// [START cloud_sql_mysql_databasesql_limit]

	// Set maximum number of connections in idle connection pool.
	dbPool.SetMaxIdleConns(5)

	// Set maximum number of open connections to the database.
	dbPool.SetMaxOpenConns(7)

	// [END cloud_sql_mysql_databasesql_limit]

	// [START cloud_sql_mysql_databasesql_lifetime]

	// Set Maximum time (in seconds) that a connection can remain open.
	dbPool.SetConnMaxLifetime(1800)

	// [END cloud_sql_mysql_databasesql_lifetime]
}

func main() {
	log.Print("Hello world sample started.")

	db, err := initSocketConnectionPool()
	if err != nil {
		log.Fatalf("initSocketConnectionPool: unable to connect: %s", err)
	}

	// Create the votes table if it does not already exist.
	if _, err = db.Exec(`CREATE TABLE IF NOT EXISTS votes
	( vote_id SERIAL NOT NULL, time_cast timestamp NOT NULL,
	candidate CHAR(6) NOT NULL, PRIMARY KEY (vote_id) );`); err != nil {
		log.Fatalf("DB.Exec: unable to create table: %s", err)
	}
	http.HandleFunc("/", handler)

	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}

	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), nil))
}