var google.golang.org/grpc/internal/envconfig.XDSAggregateAndDNS

one use

	google.golang.org/grpc/internal/envconfig (current package)
		xds.go#L69: 	XDSAggregateAndDNS = boolFromEnv("GRPC_XDS_EXPERIMENTAL_ENABLE_AGGREGATE_AND_LOGICAL_DNS_CLUSTER", true)