NewInstancer returns a DNS SRV instancer.

NewInstancerDetailed is the same as NewInstancer, but allows users to provide an explicit lookup refresh ticker instead of a TTL, and specify the lookup function instead of using net.LookupSRV.

ErrPortZero is returned by the resolve machinery when a DNS resolver returns an SRV record with its port set to zero.

Instancer yields instances from the named DNS SRV record.

Lookup is a function that resolves a DNS SRV record to multiple addresses.