Method watchCancel

connection.go:720–743

(ctx context.Context)

}

func (mc *mysqlConn) watchCancel(ctx context.Context) error {
	if mc.watching {
		// Reach here if canceled,
		// so the connection is already invalid
		mc.cleanup()
		return nil
	}
	// When ctx is already cancelled, don't watch it.
	if err := ctx.Err(); err != nil {
		return err
	}
	// When ctx is not cancellable, don't watch it.
	if ctx.Done() == nil {
		return nil
	}
	// When watcher is not alive, can't watch it.
	if mc.watcher == nil {
		return nil
	}

	mc.watching = true
	mc.watcher <- ctx
	return nil
}

func (mc *mysqlConn) startWatcher() {
	watcher := make(chan context.Context, 1)