fixing defaullt

dbcon/postgresql.go

@@ -338,7 +338,7 @@ func generateSQLFromStorage(tableName string, columnAndValues interface{}) strin
 		}
 
 		nullable := field.Tag.Get("sql-nullable")
-		if nullable == "true" {
+		if nullable == "false" {
 			nullable = "not null"
 		} else {
 			nullable = ""