rpc: add error when call result parameter is not addressable (#20638)

rpc/client.go

@@ -276,6 +276,9 @@ func (c *Client) Call(result interface{}, method string, args ...interface{}) er
 // The result must be a pointer so that package json can unmarshal into it. You
 // can also pass nil, in which case the result is ignored.
 func (c *Client) CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error {
+	if result != nil && reflect.TypeOf(result).Kind() != reflect.Ptr {
+		return fmt.Errorf("call result parameter must be pointer or nil interface: %v", result)
+	}
 	msg, err := c.newMessage(method, args...)
 	if err != nil {
 		return err