var context.closedchan

4 uses

	context (current package)
		context.go#L299: 	if done == closedchan || done == nil {
		context.go#L336: var closedchan = make(chan struct{})
		context.go#L339: 	close(closedchan)
		context.go#L405: 		c.done = closedchan