How to use http Response method Read in go?

It's been a while since I dealt with go and I seem to have forgotten how to read the docs.

If I do a get request like this...

resp, err := http.Get("https://example.com")

I then see that the response has a Body that is of an io.ReadCloser type (https://golang.org/pkg/io/#ReadCloser). I see the ReadCloser is an interface to Reader and Closer.

When I look at the Reader interface I see it has a Read method that reads bytes into p (https://golang.org/pkg/io/#Reader).

To recap, the http Response has a body which is a io.ReadCloser Interface which itself contains a Reader interface which has a Read method.

When I try this I would expect to Read the response bytes into HTML, but I see nothing...

var html []byte
num, err := resp.Body.Read(html)
fmt.Println("\n\thtml: ", html)
fmt.Printf("\n\tnum: %v, err: %v\n", num, err)

Output:

html:  []
num: 0, err: <nil>

What am I missing here?

short answer: You are passing a slice html where its len would be '0' and Read reads up to len(html) bytes into html

Here is snippet from https://golang.org/pkg/io/#Reader
> Read reads up to len(p) bytes into p. It returns the number of bytes
> read (0 <= n <= len(p)) and any error encountered. Even if Read
> returns n < len(p), it may use all of p as scratch space during the
> call. If some data is available but not len(p) bytes, Read
> conventionally returns what is available instead of waiting for more.

Now what you may do use ioutil and update the code as

body, err := ioutil.ReadAll(resp.Body)

Code

package main

import (
	"fmt"
	"io/ioutil"
	"net/http"
)

func main() {
	resp, err := http.Get("http://httpbin.org/ip")
	if err != nil {
		fmt.Println("Error making request", err.Error())
		return
	}
	defer resp.Body.Close()
	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		fmt.Println("Error reading response", err.Error())
		return
	}
	fmt.Println("Response\n", string(body))
}

Here is play link, in go playground HTTP requests won't work it is a security precaution so you may test this in your machine

Try to use "io/ioutil" package:

import "io/ioutil"
...
body, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
fmt.Println(string(body)

You're missing a good helper and friend ReadAll()

Your code should looks like this:

import "io/ioutil"

resp, err := http.Get("https://example.com")
// check err

defer resp.Body.Close() // we have to close Body if we want to reuse the connection

html, err := ioutil.ReadAll(resp.Body)
// check err

fmt.Println(string(html))