Remove mojo/go - this is being developed in the mojo repo

mojo/go/system/impl/core_impl.go

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package impl
-
-/*
-#include "mojo/public/platform/native/system_thunks.h"
-*/
-import "C"
-import "mojo/public/go/mojo/edk/system"
-
-type CoreImpl struct {
-}
-
-func (c CoreImpl) GetTimeTicksNow() int64 {
-        return (int64)(C.MojoGetTimeTicksNow())
-}
-
-var lazyInstance *CoreImpl = nil
-
-func GetCore() system.Core {
-        if lazyInstance == nil {
-                lazyInstance = new(CoreImpl)
-        }
-        return lazyInstance
-}