vendorify compiletime deps
diff --git a/go/vendor/golang.org/x/sync/errgroup/errgroup.go b/go/vendor/golang.org/x/sync/errgroup/errgroup.go
new file mode 100644
index 0000000..533438d
--- /dev/null
+++ b/go/vendor/golang.org/x/sync/errgroup/errgroup.go
@@ -0,0 +1,67 @@
+// Copyright 2016 The Go 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 errgroup provides synchronization, error propagation, and Context
+// cancelation for groups of goroutines working on subtasks of a common task.
+package errgroup
+
+import (
+ "sync"
+
+ "golang.org/x/net/context"
+)
+
+// A Group is a collection of goroutines working on subtasks that are part of
+// the same overall task.
+//
+// A zero Group is valid and does not cancel on error.
+type Group struct {
+ cancel func()
+
+ wg sync.WaitGroup
+
+ errOnce sync.Once
+ err error
+}
+
+// WithContext returns a new Group and an associated Context derived from ctx.
+//
+// The derived Context is canceled the first time a function passed to Go
+// returns a non-nil error or the first time Wait returns, whichever occurs
+// first.
+func WithContext(ctx context.Context) (*Group, context.Context) {
+ ctx, cancel := context.WithCancel(ctx)
+ return &Group{cancel: cancel}, ctx
+}
+
+// Wait blocks until all function calls from the Go method have returned, then
+// returns the first non-nil error (if any) from them.
+func (g *Group) Wait() error {
+ g.wg.Wait()
+ if g.cancel != nil {
+ g.cancel()
+ }
+ return g.err
+}
+
+// Go calls the given function in a new goroutine.
+//
+// The first call to return a non-nil error cancels the group; its error will be
+// returned by Wait.
+func (g *Group) Go(f func() error) {
+ g.wg.Add(1)
+
+ go func() {
+ defer g.wg.Done()
+
+ if err := f(); err != nil {
+ g.errOnce.Do(func() {
+ g.err = err
+ if g.cancel != nil {
+ g.cancel()
+ }
+ })
+ }
+ }()
+}