Clean up old Go 1.10 build tags

pgx requires Go modules which requires at least Go 1.11 so there is no
use in build tags to support older Go versions.

stdlib/sql.go

@@ -114,6 +114,59 @@ var (
 	fakeTxConns map[*pgx.Conn]*sql.Tx
 )
 
+// OptionOpenDB options for configuring the driver when opening a new db pool.
+type OptionOpenDB func(*connector)
+
+// OptionAfterConnect provide a callback for after connect.
+func OptionAfterConnect(ac func(context.Context, *pgx.Conn) error) OptionOpenDB {
+	return func(dc *connector) {
+		dc.AfterConnect = ac
+	}
+}
+
+func OpenDB(config pgx.ConnConfig, opts ...OptionOpenDB) *sql.DB {
+	c := connector{
+		ConnConfig:   config,
+		AfterConnect: func(context.Context, *pgx.Conn) error { return nil }, // noop after connect by default
+		driver:       pgxDriver,
+	}
+
+	for _, opt := range opts {
+		opt(&c)
+	}
+
+	return sql.OpenDB(c)
+}
+
+type connector struct {
+	pgx.ConnConfig
+	AfterConnect func(context.Context, *pgx.Conn) error // function to call on every new connection
+	driver       *Driver
+}
+
+// Connect implement driver.Connector interface
+func (c connector) Connect(ctx context.Context) (driver.Conn, error) {
+	var (
+		err  error
+		conn *pgx.Conn
+	)
+
+	if conn, err = pgx.ConnectConfig(ctx, &c.ConnConfig); err != nil {
+		return nil, err
+	}
+
+	if err = c.AfterConnect(ctx, conn); err != nil {
+		return nil, err
+	}
+
+	return &Conn{conn: conn, driver: c.driver, connConfig: c.ConnConfig}, nil
+}
+
+// Driver implement driver.Connector interface
+func (c connector) Driver() driver.Driver {
+	return c.driver
+}
+
 // GetDefaultDriver returns the driver initialized in the init function
 // and used when the pgx driver is registered.
 func GetDefaultDriver() driver.Driver {