initialize node data maps

chord/client.go

@@ -94,6 +94,7 @@ func Join(ctx context.Context, cl Client, addr netip.AddrPort, np Peer) (*Node,
 		self:    self,
 		succ:    s,
 		fingers: make([]Peer, 0, 8*len(ID{})),
+		data:    make(map[ID]string),
 	}
 	return r, nil
 }

chord/topology.go

@@ -205,6 +205,7 @@ func Create(addr netip.AddrPort) (*Node, error) {
 		self:    self,
 		succ:    []Peer{self}[:1:1], // extra cautious about capacity
 		fingers: make([]Peer, 0, len(ID{})*8),
+		data:    make(map[ID]string),
 	}
 	return n, nil
 }