os.OpenFile权限问题测试

Question

I'm currently having a problem with os.OpenFile. It just gives me "permission denied" when i run my go test.

type log struct {
    Message   string
    Source    string
    Timestamp time.Time
    ErrorCode ErrorCode
}

type ErrorCode int

const (
    Info ErrorCode = 1 + iota
    Warning
    Error
)

func (errorCode ErrorCode) String() string {
    switch errorCode {
    case Info:
            return "Info"
    case Warning:
            return "Warning"
    case Error:
            return "Error"
    }
    return "Type not found"
}

func writeToLog(logItem log) {
    err := os.Chdir("..")
    if err != nil {
            fmt.Println("Can't change working directory")
    }
    err = os.Mkdir("logs", os.FileMode(0777))
    if err != nil && os.IsNotExist(err) {
            fmt.Println("Can't create log directory")
    }
    f, err := os.OpenFile("logs/log.txt",
            os.O_WRONLY|os.O_CREATE|os.O_APPEND, os.FileMode(0666))
    if err != nil {
            fmt.Println("Can't find logfile")
            fmt.Println(err)
    }
    defer f.Sync()
    defer f.Close()

    f.WriteString(logItem.ErrorCode.String() + logItem.Source +
            logItem.Message + logItem.Timestamp.String())
}

Output:

Can't find logfile
open logs/log.txt: permission denied
Can't find logfile
open logs/log.txt: permission denied

What am I doint wrong? It seems like OpenFile doesn't set my permissions correctly (-rw-r--r--).

Thanks in advance