database: Close query rows before returning

cmd/contact-auditor/main.go

@@ -130,6 +130,14 @@ func (c contactAuditor) run(ctx context.Context, resChan chan *result) error {
 			resChan <- &result{id, contacts, createdAt}
 		}
 	}
+
+	err = rows.Err()
+	if err != nil {
+		// It's okay to return here, an abnormal termination automatically calls
+		// rows.Close(): http://go-database-sql.org/errors.html
+		return fmt.Errorf("querying db: %w", err)
+	}
+
 	// Ensure the query wasn't interrupted before it could complete.
 	err = rows.Close()
 	if err != nil {

db/multi.go

@@ -124,6 +124,13 @@ func (mi *MultiInserter) Insert(ctx context.Context, queryer Queryer) ([]int64,
 		}
 	}
 
+	err = rows.Err()
+	if err != nil {
+		// It's okay to return here, an abnormal termination automatically calls
+		// rows.Close(): http://go-database-sql.org/errors.html
+		return nil, fmt.Errorf("querying db: %w", err)
+	}
+
 	// Hack: sometimes in unittests we make a mock Queryer that returns a nil
 	// `*sql.Rows`. A nil `*sql.Rows` is not actually valid— calling `Close()`
 	// on it will panic— but here we choose to treat it like an empty list,

test/db.go

@@ -122,5 +122,15 @@ func allTableNamesInDB(ctx context.Context, db CleanUpDB) ([]string, error) {
 		}
 		ts = append(ts, tableName)
 	}
-	return ts, r.Err()
+	err = r.Err()
+	if err != nil {
+		// It's okay to return here, an abnormal termination automatically calls
+		// rows.Close(): http://go-database-sql.org/errors.html
+		return nil, err
+	}
+	err = r.Close()
+	if err != nil {
+		return nil, err
+	}
+	return ts, nil
 }