net/http: changing Transport.Dial to DialContext opts in to HTTP/2

[EvanMGates]

What did you do?

We changed http.Client from using the deprecated transport.Dial function to its replacement, transport.DialContext.

What did you expect to see?

Dial and DialContext should behave similarly when using the same parameters.

What did you see instead?

Using DialContext causes Transport to be configured for http/2. The custom dialer DialContext should not automatically enable http2 as specified in the comment at https://github.com/golang/go/blob/go1.10/src/net/http/transport.go#L228.

Does this issue reproduce with the latest release (go1.10.3)?

We noticed this issue in Go 1.10.2 and the offending code hasn't changed in Go 1.10.3.

System details

We deploy our code on linux/amd64.

We will submit a patch for this issue shortly.

[andybons]

@bradfitz

[gopherbot]

Change https://golang.org/cl/130256 mentions this issue: net/http: restrict automatic HTTP/2 transport when using DialContext

[riking]

I thought this was specified in reverse, that using Dial instead of DialContext blocks the use of h2?

[gopherbot]

Change https://golang.org/cl/172299 mentions this issue: net/http: rename to ForceAttemptHTTP2