Golang HTTP Request types

Question

The "net/http" golang package has a response type which I find confusing. It defines a member Body io.ReadCloser which requires an additional call to some form of an io writer to process. Why did the developers not choose to make the Body a []bytes or a string? These seem like much more obvious, natural choices to me.

Answer 1

An HTTP response body is a stream of bytes on the network connection. The io.Reader type is Go's representation of a stream of bytes. The Response.Body field is typed as io.ReadCloser which is an io.Reader with a Close() method.

An advantage of io.Reader over string and []byte is that the application can stream through the response without loading the entire response in memory.

Use io.ReadAll to read the io.Reader's data to a []byte.

Here's a convenient helper function converting the (*http.Response, error) return values from the net/http functions to a []byte:

func bodyBytes(r *http.Response, err error) (*http.Response, []byte, error) {
    if err != nil {
        return r, nil, err
    }
    b, err := io.ReadAll(r.Body)
    r.Body.Close()
    return r, b, err
}

Use the function like this:

 r, b, err := bodyBytes(http.Get("http://example.com"))
 if err != nil {
     // insert error handling here
 }
 // r is an *http.Response, with closed body
 // b is a []byte containing the body