Semantic way of http.Response receiver functions in Go - go

Question

I just started learning GO and wrote this piece of code that writes an http.Response.Body to os.Stdout or to a file, but I'm not happy about the semantics of this.
I want the http.Response struct to have these receiver functions, so I can use it more easily throughout the entire app.
I know that the answers might get flagged as opinionated, but I still wonder, is there a better way of writing this?
Is there some sort of best practice?
package main
import (
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
)
type httpResp http.Response
func main() {
res, err := http.Get("http://www.stackoverflow.com")
if err != nil {
fmt.Println("Error: ", err)
os.Exit(1)
}
defer res.Body.Close()
response := httpResp(*res)
response.toFile("stckovrflw.html")
response.toStdOut()
}
func (r httpResp) toFile(filename string) {
str, err := ioutil.ReadAll(r.Body)
if err != nil {
panic(err)
}
ioutil.WriteFile(filename, []byte(str), 0666)
}
func (r httpResp) toStdOut() {
_, err := io.Copy(os.Stdout, r.Body)
if err != nil {
panic(err)
}
}
On a side note, is there a way to make the http.Get method spit out a custom type that already has access to these receiver functions without the need for casting? So i could do something like this:
func main() {
res, err := http.Get("http://www.stackoverflow.com")
if err != nil {
fmt.Println("Error: ", err)
os.Exit(1)
}
defer res.Body.Close()
res.toFile("stckovrflw.html")
res.toStdOut()
}
Thanks!

Answer 1

You don't have to implement these functions. *http.Response already implements io.Writer:
Write writes r to w in the HTTP/1.x server response format, including the status line, headers, body, and optional trailer.
package main
import (
"net/http"
"os"
)
func main() {
r := &http.Response{}
r.Write(os.Stdout)
}
In the example above, the zero value prints:
HTTP/0.0 000 status code 0
Content-Length: 0
Playground: https://play.golang.org/p/2AUEAUPCA8j
In case you need additional business logic in the write methods, you can embed *http.Response in your defined type:
type RespWrapper struct {
*http.Response
}
func (w *RespWrapper) toStdOut() {
_, err := io.Copy(os.Stdout, w.Body)
if err != nil {
panic(err)
}
}
But then you must construct a variable of type RespWrapper with the *http.Response:
func main() {
// resp with a fake body
r := &http.Response{Body: io.NopCloser(strings.NewReader("foo"))}
// or r, _ := http.Get("example.com")
// construct the wrapper
wrapper := &RespWrapper{Response: r}
wrapper.toStdOut()
}
is there a way to make the http.Get method spit out a custom type
No, the return types of http.Get are (resp *http.Response, err error), that's part of the function signature, you can't change it.