mark CopyDone as frontend too

copy_done.go

@@ -10,6 +10,9 @@ type CopyDone struct {
 // Backend identifies this message as sendable by the PostgreSQL backend.
 func (*CopyDone) Backend() {}
 
+// Frontend identifies this message as sendable by a PostgreSQL frontend.
+func (*CopyDone) Frontend() {}
+
 // Decode decodes src into dst. src must contain the complete message with the exception of the initial 1 byte message
 // type identifier and 4 byte message length.
 func (dst *CopyDone) Decode(src []byte) error {