api request get body and parse json

package main

import (
    "encoding/json"
    "fmt"
    "io"
    "io/ioutil"
    "log"
    "net/http"
)

type people struct {
    Number int `json:"number"`
}

func main() {
    url := "http://api.open-notify.org/astros.json"

    headers := map[string]string{
        "User-Agent": "learninggo",
    }

    body, err := callApi(url, http.MethodGet, nil, headers)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println(string(body))

    people1 := people{}
    jsonErr := json.Unmarshal(body, &people1)
    if jsonErr != nil {
        log.Fatal(jsonErr)
    }

    fmt.Println(people1.Number)
}

// callApi makes request to url endpoint
func callApi(url string, method string, reqBody io.Reader, headers map[string]string) ([]byte, error) {
    req, err := http.NewRequest(method, url, reqBody)
    if err != nil {
        log.Fatal(err)
    }

    for key, value := range headers {
        req.Header.Set(key, value)
    }

    var client http.Client
    res, getErr := client.Do(req)
    if getErr != nil {
        return nil, getErr
    }

    if res.Body != nil {
        defer res.Body.Close()
    }

    resBody, readErr := ioutil.ReadAll(res.Body)
    if readErr != nil {
        return nil, getErr
    }

    return resBody, nil
}