Both Server and Transport implement "HTTP/2 with prior knowledge"
as described in RFC 9113, section 3.3. Neither supports the
deprecated HTTP/2 upgrade mechanism (RFC 7540, section 3.2 "h2c").
For Server, UnencryptedHTTP2 controls whether the server
will accept HTTP/2 connections on unencrypted ports.
When enabled, the server checks new connections for
the HTTP/2 preface and routes them appropriately.
For Transport, enabling UnencryptedHTTP2 and disabling HTTP1
causes http:// requests to be made over unencrypted HTTP/2
connections.
For #67816
Change-Id: I2763c4cdec1c2bc6bb8157edb93b94377de8a59b
Reviewed-on: https://go-review.googlesource.com/c/go/+/622976
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>