LookupParallel performs lookup for IP address of host with all resolvers concurrently.

NewDialContext returns a DialHandler that dials addrs and returns the first successful connection.

ResolveDialContext returns a DialHandler that uses addresses resolved from u using resolvers.

ErrNoResolvers is returned when zero resolvers specified.

Resolver resolves the hostnames to IP addresses.

DialHandler is a dial function for creating unencrypted network connections to the upstream server.