http: Log server errors

cmd/echoip/main.go

@@ -29,6 +29,11 @@ func (f *multiValueFlag) Set(v string) error {
 	return nil
 }
 
+func init() {
+	log.SetPrefix("echoip: ")
+	log.SetFlags(log.Lshortfile)
+}
+
 func main() {
 	countryFile := flag.String("f", "", "Path to GeoIP country database")
 	cityFile := flag.String("c", "", "Path to GeoIP city database")
@@ -47,7 +52,6 @@ func main() {
 		return
 	}
 
-	log := log.New(os.Stderr, "echoip: ", 0)
 	r, err := geo.Open(*countryFile, *cityFile, *asnFile)
 	if err != nil {
 		log.Fatal(err)

http/http.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"html/template"
 	"io/ioutil"
+	"log"
 	"path/filepath"
 	"strings"
 
@@ -383,6 +384,9 @@ func wrapHandlerFunc(f http.HandlerFunc) appHandler {
 func (fn appHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	if e := fn(w, r); e != nil { // e is *appError
 		// When Content-Type for error is JSON, we need to marshal the response into JSON
+		if e.Code/100 == 5 {
+			log.Println(e.Error)
+		}
 		if e.IsJSON() {
 			var data = struct {
 				Error string `json:"error"`