400 error getting oauth user token in golang?

I tried to get the ebay user token.
I've alreay gotten auth code in ebay, but can't get user token with auth code.
Code is following:

status := ctx.UserValue("status").(string)
applicationToken := string(ctx.QueryArgs().Peek("code"))
log.Println("ApplicationToken: ", applicationToken)
log.Println("Status: ", status)
if status == "declined" {
    fmt.Printf("User doesn't give permission. Go back to your dashboard.")
    ctx.Redirect("/dashboard", fasthttp.StatusSeeOther)
}

//var appConfig = config.Config()
client := &http.Client{}

applicationTokenURLEncoded, _ := url.Parse(applicationToken)

body := url.Values{
    "grant_type":   {"authorization_code"},
    "code":         {applicationTokenURLEncoded.String()},
    "redirect_uri": {Runame},
}
reqBody := bytes.NewBufferString(body.Encode())
log.Println("Reqbody: ", reqBody)

req, _ := http.NewRequest("POST", "https://api.sandbox.ebay.com/identity/v1/oauth2/token", reqBody)


authorization := “AppID” + ":" + “CertID”
authorizationBase64 := base64.StdEncoding.EncodeToString([]byte(authorization))

req.Header.Add("Authorization", "Basic "+authorizationBase64)
req.Header.Add("Content-Type", "application/x-www-form-urlencoded")
log.Println("Body: ", req)

resp, _ := client.Do(req)
log.Println("resp: ", resp)
log.Println("ResBody: ", resp.Body)

And the error is like that:

Bad Request 400

I looks like the message isn't formed correctly (which is why the server returns 400).

When you're setting your headers you write:

req.Header.Add("Authorization", "Basic "+authorizationBase64)
req.Header.Add("Content-Type", "application/x-www-form-urlencoded")

Golang has a nice built in way to add Authorization to a Header: SetBasicAuth, which is a method of http.Request.

func (r *Request) SetBasicAuth(username, password string)

> SetBasicAuth sets the request's Authorization header to use HTTP Basic Authentication with the provided username and password.

> With HTTP Basic Authentication the provided username and password are not encrypted.

So instead of setting the Authorization Header manually, you could try:

req.SetBasicAuth("AppID”, “CertID”)

You were using something called CertID, but I think you meant ClientId and ClientSecret -- respectively user and password

<hr>

I don't know if this is the cause of your problem :). One way to help find out, is consistent error checking, see your line:

applicationTokenURLEncoded, _ := url.Parse(applicationToken)