golang http.Post请求返回响应404

I have written a go code to create a issue in a project in my github reposiory. I am using parameters as mentioned here [https://developer.github.com/v3/issues/#create-an-issue][1]

But I am getting response with status 404. Below is my code.

package main

import (
    "bytes"
    "encoding/json"
    "fmt"
    "net/http"
)

func main() {
    param := map[string]string{"title": "issue1", "body": "aassddrff", "assignee": "vigneshkm"}

    query, _ := json.Marshal(param)
    queryUrl := "https://api.github.com/repos/vigneshkm/first_repo/issues"

    fmt.Println("query:", string(query))
    resp, err := http.Post(queryUrl, "application/json", bytes.NewBuffer(query))

    fmt.Println("query_status : ", resp.StatusCode, "err : ", err)
    resp.Body.Close()
}

I am a beginner to web programming and I am not able to understand my mistake in this code. Kindly help me :)