Trying to make a HTTP request and return the result of that request in an app that uses go/gin

I just picked up Go yesterday and I was wondering how I can make an HTTP request and return the result of that request with my API made with Gin.

This is the code for the endpoint that returns the result of another request

func ProvideAccessToken(c *gin.Context) {
	body := bindings.RequestAccessTokenBody{}

	err := c.ShouldBind(&body)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		log.Println(err)
		return
	}

	if body.Code == "" || body.GrantType == "" || body.RedirectURI == "" {
		c.String(http.StatusBadRequest, "Bad Request")
		return
	}
	res, err := helpers.ExchangeCodeForToken(body.GrantType, body.RedirectURI, body.Code)

	if err != nil {
		c.JSON(res.StatusCode, gin.H{"error": err.Error()})
		return
	}
	defer res.Body.Close()
	c.Header("Content-Type", "application/json")
	c.JSON(200, res.Body)
}

This is the function that makes the HTTP request

func ExchangeCodeForToken(grantType string, redirectUri string, code string) (*http.Response, error) {
	authToken := "Basic " + encodeClientSecretAndId()
	body := url.Values{}
	body.Set("grant_type", grantType)
	body.Set("redirect_uri", redirectUri)
	body.Set("code", code)
	encodedBody := body.Encode()
	client := &http.Client{}

	r, _ := http.NewRequest(http.MethodPost, tokenUrl, strings.NewReader(encodedBody))
	r.Header.Add("Content-Type", "application/x-www-form-urlencoded")
	r.Header.Add("Authorization", authToken)
	res, err := client.Do(r)
	return res, err
}

When I use postman to make a request, the response is just an empty json like so{}.
When change the end of my ProvideAccessToken function to be

	defer res.Body.Close()
	respbody, err := ioutil.ReadAll(res.Body)
	if err != nil {
		c.JSON(res.StatusCode, gin.H{"error": err.Error()})
		return
	}
	c.Header("Content-Type", "application/json")
	c.JSON(200, string(respbody))

I get this as my result "{\"error\":\"invalid_grant\",\"error_description\":\"Authorization code expired\"}", which is correct but it has the weird formatting. I just want to return exactly what the other API returns.

The first version of the program encodes the response body value as JSON. The response is {} because there are no exported fields in the response body. It's not what you want.

The second version of the program encodes the JSON response as a JSON. The weird formatting is the escaping of the " in the original JSON.

Write the data as is to the response. Here's a modification to the second version of the program:

defer res.Body.Close()
respbody, err := ioutil.ReadAll(res.Body)
if err != nil {
    c.JSON(res.StatusCode, gin.H{"error": err.Error()})
    return
}
c.Data(200, "application/json", respbody) // <-- note this line

You can also copy from one response to the other:

defer res.Body.Close()
c.DataFromReader(200, res.ContentLength, "application/json", res.Body, nil)