Consider deprecating Dial and DialContext and replacing with a NewClient

[dfawley]

Dial and DialContext have several differences from how gRPC works in other languages. A NewClient function that works more like other languages would differ in at least two ways:

1. Default to DNS resolver instead of passthrough.
2. Make target compliant with RFC 3986 (Revise URI scheme parsing to be RFC 3986 compliant #1911).
3. Start IDLE instead of CONNECTING.

If we create a NewClient, we'd probably also want to make matching ClientOptions instead of DialOptions, as some DialOptions (e.g. WithBlock or WithTimeout) do not make sense when not dialing synchronously.

[nhooyr]

Default to DNS resolver instead of passthrough.

Could you elaborate on what passthrough would be? Wouldn't all Dial's use a DNS resolver?

[dfawley]

Passthrough sends the entire target string (after "passthrough:///") to the dialer as the address, verbatim.

A DNS resolver would resolve the target (after "dns:///"), turn it into IP addresses & ports, and those would be handed to the dialer.

It just so happens that the default dialer (net.Dial) is able to do DNS name resolution, and so passing "google.com:22" will work just fine with it.

However, this passthrough method means we can't do things like load-balance across all the DNS results for that name.

You can see more about the resolver/balancer design in the gRFC here: https://github.com/grpc/proposal/blob/master/L9-go-resolver-balancer-API.md