When creating a container one can specify custom DNS settings: https://godoc.org/github.com/docker/engine-api/types/container#HostConfig - specifically DNS, DNSOptions and DNSSearch

There is no equivalent in the https://godoc.org/github.com/docker/engine-api/types/swarm#ServiceSpec