restful protocol transport dial cause io timeout

[otis95]

Environment

• Client: Dubbo-go, v1.5.9
• Protocol: rest
• Registry: zookeeper

Issue description

https://github.com/apache/dubbo-go/blob/main/protocol/rest/client/client_impl/resty_client.go#L59
err = c.SetDeadline(time.Now().Add(restOption.RequestTimeout))
http连接池复用tcp连接时，因为设置了deadline，resp未返回直接抛出io timeout。

[otis95]

推荐调整为：

func NewRestyClient(restOption *client.RestOptions) client.RestClient {
	client := resty.New()
	client.SetTransport(
		&http.Transport{
			DialContext: (&net.Dialer{
				Timeout: restOption.ConnectTimeout,
			}).DialContext,
			IdleConnTimeout: 90 * time.Second,
		}).SetTimeout(restOption.RequestTimeout)
	return &RestyClient{
		client: client,
	}
}

1. 通过配置IdleConnTimeout超时来回收空闲链接。
2. 通过client.SetTimeout来设置每次请求的超时时间。