releaseConnOnce sync.Once
	// releaseConnCache is a cache of c.closemuRUnlockCondReleaseConn
	// to save allocations in a call to grabConn.
	releaseConnCache releaseConn
}

// grabConn takes a context to implement stmtConnGrabber
// but the context is not used.
func (c *Conn) grabConn(context.Context) (*driverConn, releaseConn, error) {
	if c.done.Load() {
		return nil, nil, ErrConnDone
	}

	}
	c := new(Conn)
	ctx := context.Background()
	n := int(testing.AllocsPerRun(1000, func() {
		_, release, err := c.grabConn(ctx)
		if err != nil {
			t.Fatal(err)
		}
		release(nil)
	}))
	if n > 0 {
		t.Fatalf("Conn.grabConn allocated %v objects; want 0", n)
	}
}

func BenchmarkGrabConn(b *testing.B) {
	b.ReportAllocs()
	c := new(Conn)