cdc panic: runtime error: invalid memory address or nil pointer dereference

[fubinzh]

What did you do?

This panic is seen after #10798

What did you expect to see?

cdc no panic

What did you see instead?

{"level":"warn","ts":"2024-03-17T03:44:29.64617Z","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0038b4000/upstream-pd-0.upstream-pd-peer.cdc-airbnb-simple-tian-gcp-tps-7500530-1-808.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-03-17T03:44:35.647313Z","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0038b4000/upstream-pd-0.upstream-pd-peer.cdc-airbnb-simple-tian-gcp-tps-7500530-1-808.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-03-17T03:44:41.648666Z","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc0038b4000/upstream-pd-0.upstream-pd-peer.cdc-airbnb-simple-tian-gcp-tps-7500530-1-808.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
{"level":"warn","ts":"2024-03-17T03:46:41.939417Z","logger":"etcd-client","caller":"v3@v3.5.12/retry_interceptor.go:62","msg":"retrying of unary invoker failed","target":"etcd-endpoints://0xc003b921c0/upstream-pd-0.upstream-pd-peer.cdc-airbnb-simple-tian-gcp-tps-7500530-1-808.svc:2379","attempt":0,"error":"rpc error: code = DeadlineExceeded desc = context deadline exceeded"}
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x3878de9]

goroutine 9470229 [running]:
github.com/pingcap/tiflow/cdc/kv.(*requestedStream).receive(0xc0706b43c0, {0x5c10998, 0xc0706b52c0}, 0xc0747ea580, 0xc06e0f2980, 0x1959945?, 0xc0706b48c0?)
        github.com/pingcap/tiflow/cdc/kv/shared_stream.go:225 +0x69
github.com/pingcap/tiflow/cdc/kv.(*requestedStream).run.func3()
        github.com/pingcap/tiflow/cdc/kv/shared_stream.go:187 +0x2e
golang.org/x/sync/errgroup.(*Group).Go.func1()
        golang.org/x/sync@v0.6.0/errgroup/errgroup.go:78 +0x56
created by golang.org/x/sync/errgroup.(*Group).Go in goroutine 9470087
        golang.org/x/sync@v0.6.0/errgroup/errgroup.go:75 +0x96

Versions of the cluster

cdc version:
cdc version:
Release Version: v8.0.0
Git Commit Hash: 130403f
Git Branch: heads/refs/tags/v8.0.0
UTC Build Time: 2024-03-15 13:58:58
Go Version: go version go1.21.6 linux/amd64
Failpoint Build: false

[3AceShowHand]

The client is closed and set to nil in the goroutine a, and read by the goroutine b, the cause the panic.