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 ?