const Name … var logger … // newBuilder creates a new roundrobin balancer builder. func newBuilder() balancer.Builder { … } func init() { … } type rrPickerBuilder … func (*rrPickerBuilder) Build(info base.PickerBuildInfo) balancer.Picker { … } type rrPicker … func (p *rrPicker) Pick(balancer.PickInfo) (balancer.PickResult, error) { … }