func Serve(l net.Listener, handler http.Handler) error {
	defaultServer = NewWithServer(&http.Server{Handler: handler})
	return defaultServer.Serve(l)
}
Serve provides a graceful version of the function provided by the net/http
package. Call Close() to stop the server.
package manners
import (
	"net"
	"net/http"
)
var defaultServer *GracefulServer
func ListenAndServe(addr string, handler http.Handler) error {
	defaultServer = NewWithServer(&http.Server{Addr: addr, Handler: handler})
	return defaultServer.ListenAndServe()
}
func ListenAndServeTLS(addr string, certFile string, keyFile string, handler http.Handler) error {
	defaultServer = NewWithServer(&http.Server{Addr: addr, Handler: handler})
	return defaultServer.ListenAndServeTLS(certFile, keyFile)
}