$ go run main.go

github.com/astaxie/beego/utils

F:\GitHub\gopro\src\github.com\astaxie\beego\utils\mail.go:407: undefined: sync.Pool

github.com/astaxie/beego/logs

F:\GitHub\gopro\src\github.com\astaxie\beego\logs\log.go:138: undefined: sync.Pool F:\GitHub\gopro\src\github.com\astaxie\beego\logs\log.go:168: undefined: sync.Pool