エラー内容

undefined: balancer.PickOptions以外にも、undefined: resolver.BuildOptionや、undefined: ResolveNowOptionも同時に発生する場合がある。

# github.com/coreos/etcd/clientv3/balancer/picker
/home/reoring/go/pkg/mod/github.com/coreos/etcd@v3.3.22+incompatible/clientv3/balancer/picker/err.go:37:44: undefined: balancer.PickOptions
/home/reoring/go/pkg/mod/github.com/coreos/etcd@v3.3.22+incompatible/clientv3/balancer/picker/roundrobin_balanced.go:55:54: undefined: balancer.PickOptions
# github.com/coreos/etcd/clientv3/balancer/resolver/endpoint
/home/reoring/go/pkg/mod/github.com/coreos/etcd@v3.3.22+incompatible/clientv3/balancer/resolver/endpoint/endpoint.go:114:78: undefined: resolver.BuildOption
/home/reoring/go/pkg/mod/github.com/coreos/etcd@v3.3.22+incompatible/clientv3/balancer/resolver/endpoint/endpoint.go:182:31: undefined: resolver.ResolveNowOption

解決方法

etcdのバージョンを落とす。この場合は3.3.13まで落とすと上記エラーは発生しない。

go get go.etcd.io/etcd@v3.3.13+incompatible
go get github.com/coreos/etcd@v3.3.13+incompatible