Replace deprecated Transport.Dial with Transport.DialContext

[PaulSD]

http.Transport.Dial is deprecated. Other parts of Docker have been updated to use DialContext instead (for example: https://github.com/moby/moby/blob/master/client/options.go#L66), but go-connections is currently still using Dial.

This commit updates go-connections to use DialContext.

[AkihiroSuda]

cc @thaJeztah

[thaJeztah]

LGTM

[thaJeztah]

@jhowardmsft do you know if a new release is planned?

[ijc]

How was this change tested? For me it doesn't build:

$ go get golang.org/x/net/proxy
$ go get github.com/pkg/errors
$ go get github.com/stretchr/testify/assert
$ go test ./...
?   	github.com/docker/go-connections	[no test files]
# github.com/docker/go-connections/sockets [github.com/docker/go-connections/sockets.test]
sockets/sockets.go:34:26: dialer.DialContext undefined (type proxy.Dialer has no field or method DialContext)
sockets/sockets_unix.go:24:28: undefined: context
ok  	github.com/docker/go-connections/nat	(cached)
ok  	github.com/docker/go-connections/proxy	(cached)
FAIL	github.com/docker/go-connections/sockets [build failed]
ok  	github.com/docker/go-connections/tlsconfig	(cached)

The naive change just kicks the can a bit further down the road:

diff --git a/sockets/proxy.go b/sockets/proxy.go
index 98e9a1d..36978c8 100644
--- a/sockets/proxy.go
+++ b/sockets/proxy.go
@@ -23,7 +23,7 @@ func GetProxyEnv(key string) string {
 // DialerFromEnvironment takes in a "direct" *net.Dialer and returns a
 // proxy.Dialer which will route the connections through the proxy using the
 // given dialer.
-func DialerFromEnvironment(direct *net.Dialer) (proxy.Dialer, error) {
+func DialerFromEnvironment(direct *net.Dialer) (proxy.ContextDialer, error) {
        allProxy := GetProxyEnv("all_proxy")
        if len(allProxy) == 0 {
                return direct, nil

produces:

$ go test ./...
?   	github.com/docker/go-connections	[no test files]
ok  	github.com/docker/go-connections/nat	(cached)
# github.com/docker/go-connections/sockets [github.com/docker/go-connections/sockets.test]
sockets/proxy.go:44:3: cannot use proxyFromURL (type proxy.Dialer) as type proxy.ContextDialer in return argument:
	proxy.Dialer does not implement proxy.ContextDialer (missing DialContext method)
sockets/sockets_unix.go:24:28: undefined: context
ok  	github.com/docker/go-connections/proxy	(cached)
FAIL	github.com/docker/go-connections/sockets [build failed]
ok  	github.com/docker/go-connections/tlsconfig	(cached)

I can't see a variant of golang.org/x/net/proxy.FromURL which returns something satisfying ContextDialer directly, meaning we would have to a type cast I think and deal with possible errors from that. It also brings a dependency on the very latest x/net since golang/net@7f726ca is only from a couple of weeks ago.

[thaJeztah]

How was this change tested? For me it doesn't build

That's weird, I think CI was green 🤔

[thaJeztah]

Oh, wait; there's #61

Looking at that PR, it looks like CI isn't running 😞

[ijc]

CI doesn't appear to build, just lint and fmt...

I just spotted #61 which I suspect might be the fix.

I also missed #60 reporting this too

[ijc]

CI doesn't appear to build, just lint and fmt...

Correction: + vet which does catch the build errors (iff the CI runs)