Create a socket connection when using Go

Open a Unix socket connection to Cloud SQL for PostgreSQL by using Go's database/sql package.

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For detailed documentation that includes this code sample, see the following:

Code sample

Go

To authenticate to Cloud SQL for PostgreSQL, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

package cloudsql

import (
	"database/sql"
	"fmt"
	"log"
	"os"

	// Note: If connecting using the App Engine Flex Go runtime, use
	// "github.com/jackc/pgx/stdlib" instead, since v5 requires
	// Go modules which are not supported by App Engine Flex.
	_ "github.com/jackc/pgx/v5/stdlib"
)

// connectUnixSocket initializes a Unix socket connection pool for
// a Cloud SQL instance of Postgres.
func connectUnixSocket() (*sql.DB, error) {
	mustGetenv := func(k string) string {
		v := os.Getenv(k)
		if v == "" {
			log.Fatalf("Fatal Error in connect_unix.go: %s environment variable not set.\n", k)
		}
		return v
	}
	// Note: Saving credentials in environment variables is convenient, but not
	// secure - consider a more secure solution such as
	// Cloud Secret Manager (https://cloud.google.com/secret-manager) to help
	// keep secrets safe.
	var (
		dbUser         = mustGetenv("DB_USER")              // e.g. 'my-db-user'
		dbPwd          = mustGetenv("DB_PASS")              // e.g. 'my-db-password'
		unixSocketPath = mustGetenv("INSTANCE_UNIX_SOCKET") // e.g. '/cloudsql/project:region:instance'
		dbName         = mustGetenv("DB_NAME")              // e.g. 'my-database'
	)

	dbURI := fmt.Sprintf("user=%s password=%s database=%s host=%s",
		dbUser, dbPwd, dbName, unixSocketPath)

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

	// ...

	return dbPool, nil
}

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