Fix intermittent broken pipe issue in log

This commit fixes goharbor#4713, by adopting the suggested fix in:
go-sql-driver/mysql#529
When creating the DB instance in orm, call `SetConnMaxLifetime()`

src/common/dao/mysql.go

@@ -16,6 +16,7 @@ package dao
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/astaxie/beego/orm"
 	_ "github.com/go-sql-driver/mysql" //register mysql driver
@@ -58,7 +59,12 @@ func (m *mysql) Register(alias ...string) error {
 	}
 	conn := fmt.Sprintf("%s:%s@tcp(%s:%s)/%s", m.usr,
 		m.pwd, m.host, m.port, m.database)
-	return orm.RegisterDataBase(an, "mysql", conn)
+	if err := orm.RegisterDataBase(an, "mysql", conn); err != nil {
+		return err
+	}
+	db, _ := orm.GetDB(an)
+	db.SetConnMaxLifetime(5 * time.Minute)
+	return nil
 }
 
 // Name returns the name of MySQL