crypto/tls: add Dialer with Dial, DialContext methods

[akalin-keybase]

In go 1.7, Dialer now has DialContext, which takes a context.Context and uses it for expiration.

However, DialWithDialer just calls Dial on its given Dialer, and doesn't take a context.Context.

To be backwards compatible, probably need to provide a separate function, say, DialContextWithDialer, that is like DialWithDialer except it takes a context.Context and calls DialContext, and have DialWithDialer call DialContextWithDialer with context.Background().

It looks like as a workaround, callers can write their own DialContextWithDialer function and copy most of DialWithDialer.

[bradfitz]

The review period for Go 1.7 APIs ended 6 months ago.

The review period for Go 1.8 APIs ended approximately 3 weeks ago.

We can consider something new in crypto/tls for Go 1.9.

For now, you'll just have to dial first, and then use https://golang.org/pkg/crypto/tls/#Client to start the client handshake on the already-connected TCP (or whatever) Conn.

[rosenhouse]

I believe I have a use-case for this feature and would be curious if there's a suggested work-around.

We're trying to configure a http.Transport such that the client does extra validation of the server-provided certificate before sending any data. We want this client to compare server-provided certificate fields against values present on the req.Context. We see Transport.DialContext() but there's no Transport.DialTLSContext(), and setting a DialContext function that does TLS internally looks like it won't work.

Edit: perhaps I'm asking in the wrong issue -- this is bigger than just the crypto/tls package...

[gobwas]

Hello! Sorry for "pinging", but will this issue be landed in 1.10? Milestone is 1.10 but no NeedsFix label... Im okay with the work-around, but it looks like little dirty when I need to copy logic of adding tls.Config.ServerName from tls.DialWithDialer().

[ianlancetaylor]

@gobwas There has been no definite decision to implement this, and there is no patch. At this point I would say that it is unlikely to be fixed for 1.10. Sorry.

[gopherbot]

Change https://golang.org/cl/93255 mentions this issue: crypto/tls: add DialContextWithDialer function