var context.closedchan

4 uses

	context (current package)
		context.go#L299: 	if done == closedchan || done == nil {
		context.go#L334: var closedchan = make(chan struct{})
		context.go#L337: 	close(closedchan)
		context.go#L409: 		c.done.Store(closedchan)