Google App Engine does not support fmt. Using log instead

mode.go

@@ -5,7 +5,7 @@
 package gin
 
 import (
-	"fmt"
+	"log"
 	"os"
 )
 
@@ -58,6 +58,6 @@ func IsDebugging() bool {
 
 func debugPrint(format string, values ...interface{}) {
 	if IsDebugging() {
-		fmt.Printf("[GIN-debug] "+format, values...)
+		log.Printf("[GIN-debug] "+format, values...)
 	}
 }