net/http: test intended behavior in TestClientInsecureTransport
This test wasn't testing the HTTP/2 case, because it didn't
set NextProtos in the tls.Config.
Set "Connection: close" on requests to make sure each request
gets a new connection.
Change-Id: I1ef470e7433a602ce88da7bd7eeec502687ea857
Reviewed-on: https://go-review.googlesource.com/c/go/+/655676
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Sean Liao <sean@liao.dev>
Auto-Submit: Damien Neil <dneil@google.com> Reviewed-by: Michael Pratt <mpratt@google.com>