Bug report criteria

• This bug report is not security related, security issues should be disclosed privately via etcd maintainers.
• This is not a support request or question, support requests or questions should be raised in the etcd discussion forums.
• You have read the etcd bug reporting guidelines.
• Existing open issues along with etcd frequently asked questions have been checked and this is not a duplicate.

What happened?

watch api blocked forever even with WithRequireLeader option

What did you expect to happen?

no matter how the etcd server changes leader and restarts, as long as WithRequireLeader is set, it won't blocked

How can we reproduce it (as minimally and precisely as possible)?

1. both 'Created' and 'Canceled' in pb.WatchResponse are True
2. the client receives an err immediately after receiving the response
3. err is HaltErr or ErrNoLeader

Anything else we need to know?

clientv3/watch.go/run may

1. blocked at w.wg.Wait() in defer
2. blocked at ws.outc not be closed

Etcd version (please run commands below)

golang client version : v0.0.0-20200520232829-54ba9589114f
server version : etcd Version: 3.4.16

Etcd configuration (command line flags or environment variables)

No response

Etcd debug information (please run commands below, feel free to obfuscate the IP address or FQDN in the output)

No response

Relevant log output

No response