func (f ErrorHandlerFunc) ServeHTTP(w http.ResponseWriter, r *http.Request, err error) {
	f(w, r, err)
}
ServeHTTP calls f(w, r).
package utils
import (
	"io"
	"net"
	"net/http"
	"github.com/getlantern/errors"
	"github.com/getlantern/golog"
)
type ErrorHandler interface {
	ServeHTTP(w http.ResponseWriter, req *http.Request, err error)
}
var (
	log = golog.LoggerFor("errorhandler")
	DefaultHandler ErrorHandler = &StdHandler{}
)
type StdHandler struct {
}
func (e *StdHandler) ServeHTTP(w http.ResponseWriter, req *http.Request, err error) {
	desc := err.Error()
	cause := err
	if structured, ok := err.(errors.Error); ok {
		cause = structured.RootCause()
	}
	statusCode := http.StatusInternalServerError
	if e, ok := cause.(net.Error); ok {
		if e.Timeout() {
			statusCode = http.StatusGatewayTimeout
		} else {
			statusCode = http.StatusBadGateway
		}
	} else if cause == io.EOF {
		statusCode = http.StatusBadGateway
	}
	log.Errorf("Responding with %d due to %v: %v", statusCode, cause, desc)
	w.WriteHeader(statusCode)
	w.Write([]byte(http.StatusText(statusCode)))
}
type ErrorHandlerFunc func(http.ResponseWriter, *http.Request, error)