doc/go1.11: add note to remove CLI support for godoc

Updates #25443

Change-Id: I5e2f84f3cee6582807b2756ffac91e8583a2baec
Reviewed-on: https://go-review.googlesource.com/126737Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.11.html

@@ -313,6 +313,12 @@ func f(v interface{}) {
 
 <h3 id="godoc">Godoc</h3>
 
+<p>
+  Go 1.11 will be the last release to support <code>godoc</code>'s command-line interface.
+  In future releases, <code>godoc</code> will only be a web server. Users should use
+  <code>go</code> <code>doc</code> for command-line help output instead.
+</p>
+
 <p><!-- CL 85396, CL 124495 -->
   The <code>godoc</code> web server now shows which version of Go introduced
   new API features. The initial Go version of types, funcs, and methods are shown