go vet && golint

tracecallback_noimpl.go

@@ -4,6 +4,7 @@ package sqlite3
 
 import "errors"
 
+// RegisterAggregator register the aggregator.
 func (c *SQLiteConn) RegisterAggregator(name string, impl interface{}, pure bool) error {
 	return errors.New("This feature is not implemented")
 }