// @author <cnblogs.com/farwish>

c := colly.NewCollector()

c.OnRequest(func(request *colly.Request) {
    request.Headers.Set("Content-Type", "application/x-www-form-urlencoded")
})

c.OnHTML("a", func(element *colly.HTMLElement) {
    //
})

requestData := map[string]string {
    "abc":    "xxx",
}

err := c.Post(url, requestData)
if err != nil {
    log.Fatal(err)
}