403 Forbidden but postman return 200

[C-L-STARK]

https://pixabay.com/zh/photos/search/?order=ec&pagi=1

we want use colly to get some images from this website. but we got 403; use postman return 200. why ?

package main

import (
    "strconv"

    "github.com/gocolly/colly"
)

func main() {
    c := colly.NewCollector(
        // MaxDepth is 2, so only the links on the scraped page
        // and links on those pages are visited
        colly.Async(true),
    )
    c.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/39.0.2171.95 Safari/537.36 OPR/26.0.1656.60"
    c.Limit(&colly.LimitRule{DomainGlob: "*", Parallelism: 4})

    // Find and visit all links
    c.OnHTML("script", func(e *colly.HTMLElement) {
        if e.Attr("type") == "application/ld+json" {
            // parse inner content
            content := e.Text
            println(content)
        } else {
            println(e.Text)
        }
        e.Request.Visit(e.Attr("src"))
    })

    c.OnRequest(func(r *colly.Request) {
        println(r.URL.String())
    })

    c.OnError(func(r *colly.Response, e error) {
        println(r.StatusCode)
        println(e.Error())
    })

    for i := 1; i < 2; i++ {
        c.Visit("https://pixabay.com/zh/photos/search/?order=ec&pagi=" + strconv.Itoa(i))
    }

    c.Wait()
}

[Running] go run "~/pixabay_spider/main.go"
https://pixabay.com/zh/photos/search/?order=ec&pagi=1
403
Forbidden

[C-L-STARK]

it seems like: the website use http2.0, but colly send http1.1;

how to set a http2 proxy ?