net/http: check for nil, nil return from DialContext as well as Dial
Change-Id: I3b6dd9c40b3c10db2eda6a25b9d556c9c3733bbc
GitHub-Last-Rev:
fd9b0c4193511a75b4a0073f37aa3116db23a46f
GitHub-Pull-Request: golang/go#57448
Reviewed-on: https://go-review.googlesource.com/c/go/+/458876
Reviewed-by: Javad Rajabzadeh <ja7ad@live.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>