net: add tests for forceGoDNS and forceCgoDNS
There was a bug in forceCgoDNS (CL 479416), it was fixed by CL 487196, so
add a test case for it.
Change-Id: I2010374451ef236dc2898d9e9ea006eb8b40d02e
GitHub-Last-Rev:
34a84fad33404c66c3ee20cb63803214c42e991d
GitHub-Pull-Request: golang/go#59922
Reviewed-on: https://go-review.googlesource.com/c/go/+/491255
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>