修复postgresql中int64类型id字段在数据库建表字段数据类型错误问题

postgres_dialect.go

@@ -783,6 +783,11 @@ func (db *postgres) SqlType(c *core.Column) string {
 			return core.Serial
 		}
 		return core.Integer
+	case core.BigInt:
+		if c.IsAutoIncrement {
+			return core.BigSerial
+		}
+		return core.BigInt
 	case core.Serial, core.BigSerial:
 		c.IsAutoIncrement = true
 		c.Nullable = false