func UntilSignal(parent context.Context, sig ...os.Signal) *Context {
ctx := new(Context)
ctx.parent = parent
- ctx.done = make(chan struct{})
if err := parent.Err(); err != nil {
- close(ctx.done)
+ ctx.done = alreadyclosed
ctx.err = err
return ctx
}
+ ctx.done = make(chan struct{})
ctx.c = make(chan os.Signal, 1)
signal.Notify(ctx.c, sig...)
go ctx.wait(sig...)
s.m.Unlock()
return err
}
+
+// Reuse the same channel for all contexts which begin life already
+// completed.
+var alreadyclosed = make(chan struct{})
+
+func init() {
+ close(alreadyclosed)
+}