Close can panic #236
Description
Our CI has failed a couple of times lately with this error:
panic: sync: negative WaitGroup counter
goroutine 3436 [running]:
sync.(*WaitGroup).Add(0xc000051ad8, 0xffffffffffffffff)
/usr/local/go/src/sync/waitgroup.go:74 +0x20c
sync.(*WaitGroup).Done(...)
/usr/local/go/src/sync/waitgroup.go:99
github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap.(*Conn).Close(0xc000051a80)
/go/src/github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap/conn.go:221 +0x293
github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap.(*Conn).reader.func1(0xc000d8cf36, 0xc000051a80)
/go/src/github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap/conn.go:479 +0x81
github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap.(*Conn).reader(0xc000051a80)
/go/src/github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap/conn.go:495 +0x3da
created by github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap.(*Conn).Start
/go/src/github.com/hashicorp/vault/vendor/github.com/go-ldap/ldap/conn.go:190 +0x51
We're using v3.0.2 of go-ldap/ldap. It looks like this is happening because it's possible for Close to be called from reader's defer, before Start has been able to call wgClose.Add.