golng获取url和resp.Body.Close（）

Question

I am looking for go code to fetch url and in most of the cases this the code for fetching url on go :

func main() {
    for _, url := range os.Args[1:] {
        resp, err := http.Get(url)
        if err != nil {
            fmt.Fprintf(os.Stderr, "fetch: %v
", err)
            os.Exit(1)
        }
        b, err := ioutil.ReadAll(resp.Body)
        resp.Body.Close()
        if err != nil {
            fmt.Fprintf(os.Stderr, "fetch: reading %s: %v
", url, err)
            os.Exit(1)
        }
        fmt.Printf("%s", b)
    }
}

my question why needed here resp.Body.Close() and whay this exactly doing ?

Answer 1

If you dig into the http docs https://golang.org/pkg/net/http/

The Get method used to make the resp is a Response

 func (c *Client) Get(url string) (resp *Response, err error)

In the Response source:

        // Body represents the response body.
        //
        // The response body is streamed on demand as the Body field
        // is read. If the network connection fails or the server
        // terminates the response, Body.Read calls return an error.
        //
        // The http Client and Transport guarantee that Body is always
        // non-nil, even on responses without a body or responses with
        // a zero-length body. It is the caller's responsibility to
        // close Body. The default HTTP client's Transport may not
        // reuse HTTP/1.x "keep-alive" TCP connections if the Body is
        // not read to completion and closed.
        //
        // The Body is automatically dechunked if the server replied
        // with a "chunked" Transfer-Encoding.
        Body io.ReadCloser

So the Close() tidies up the resources that are used to get the Body

If this isn't done the Response (resp) won't be able to do "keep-alive" and I guess there is a chance that some of the resources in the Response won't be able to be recycled