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

one use

	google.golang.org/grpc/internal/envconfig (current package)
		envconfig.go#L121: 	EnablePriorityLBChildPolicyCache = boolFromEnv("GRPC_EXPERIMENTAL_ENABLE_PRIORITY_LB_CHILD_POLICY_CACHE", false)