func keyof(req *http.Request) uint64 {
	return murmur3.Sum64([]byte(
		req.Method + ":" + req.URL.String(),
	))
}
Keyof returns a cache key of req.
package antcache
import (
	"net/http"
	"strings"
	"time"
	"github.com/spaolacci/murmur3"
)
func merge(a http.Header, b http.Header) {
	for key := range b {
		switch key {
		case "Keep-Alive":
		case "Proxy-Authenticate":
		case "Proxy-Authorization":
		case "Te":
		case "Trailers":
		case "Transfer-Encoding":
		case "Upgrade":
		default:
			a[key] = b[key]
		}
	}
}