net/http: clarify Handler panic behavior across HTTP versions

Updates #18997

Change-Id: Ib1961a4c26b42f99b98b255beb7e2a74b632e0c1
Reviewed-on: https://go-review.googlesource.com/48551Reviewed-by: Joe Shaw <joe@joeshaw.org>
Reviewed-by: Tom Bergan <tombergan@google.com>

src/net/http/server.go

@@ -75,9 +75,10 @@ var (
 // If ServeHTTP panics, the server (the caller of ServeHTTP) assumes
 // that the effect of the panic was isolated to the active request.
 // It recovers the panic, logs a stack trace to the server error log,
-// and hangs up the connection. To abort a handler so the client sees
-// an interrupted response but the server doesn't log an error, panic
-// with the value ErrAbortHandler.
+// and either closes the network connection or sends an HTTP/2
+// RST_STREAM, depending on the HTTP protocol. To abort a handler so
+// the client sees an interrupted response but the server doesn't log
+// an error, panic with the value ErrAbortHandler.
 type Handler interface {
 	ServeHTTP(ResponseWriter, *Request)
 }