net/http: add Protocols field to Server and Transport

Support configuring which HTTP version(s) a server or client use
via an explicit set of protocols. The Protocols field takes
precedence over TLSNextProto and ForceAttemptHTTP2.

Fixes #67814

Change-Id: I09ece88f78ad4d98ca1f213157b5f62ae11e063f
Reviewed-on: https://go-review.googlesource.com/c/go/+/607496
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/net/http/http_test.go b/src/net/http/http_test.go
index 777634bbb2..5aba3ed5a6 100644
--- a/src/net/http/http_test.go
+++ b/src/net/http/http_test.go
@@ -187,6 +187,28 @@ func TestNoUnicodeStrings(t *testing.T) {
 	}
 }
 
+func TestProtocols(t *testing.T) {
+	var p Protocols
+	if p.HTTP1() {
+		t.Errorf("zero-value protocols: p.HTTP1() = true, want false")
+	}
+	p.SetHTTP1(true)
+	p.SetHTTP2(true)
+	if !p.HTTP1() {
+		t.Errorf("initialized protocols: p.HTTP1() = false, want true")
+	}
+	if !p.HTTP2() {
+		t.Errorf("initialized protocols: p.HTTP2() = false, want true")
+	}
+	p.SetHTTP1(false)
+	if p.HTTP1() {
+		t.Errorf("after unsetting HTTP1: p.HTTP1() = true, want false")
+	}
+	if !p.HTTP2() {
+		t.Errorf("after unsetting HTTP1: p.HTTP2() = false, want true")
+	}
+}
+
 const redirectURL = "/thisaredirect细雪withasciilettersのけぶabcdefghijk.html"
 
 func BenchmarkHexEscapeNonASCII(b *testing.B) {