mysql: Fix ColumnNumber() panic with nil Resultset

Author: dveeden

mysql/resultset.go

@@ -87,6 +87,9 @@ func (r *Resultset) RowNumber() int {
 }
 
 func (r *Resultset) ColumnNumber() int {
+	if r == nil {
+		return 0
+	}
 	return len(r.Fields)
 }
 

mysql/resultset_test.go

@@ -0,0 +1,10 @@
+package mysql
+
+import "testing"
+
+func TestColumnNumber(t *testing.T) {
+	r := Result{}
+	// Make sure ColumnNumber doesn't panic if ResultSet is nil
+	// https://github.com/go-mysql-org/go-mysql/issues/964
+	r.ColumnNumber()
+}