panic-log.go

if opts.LogFile != "" {
        logFp, err := os.OpenFile(opts.LogFile, os.O_WRONLY | os.O_APPEND | os.O_CREATE, 0600)
        checkError(fmt.Sprintf("error opening %s", opts.LogFile), err)
        
        defer logFp.Close()
        
        // ensure panic output goes to log file
        syscall.Dup2(int(logFp.Fd()), 1)
        syscall.Dup2(int(logFp.Fd()), 2)
        
        // log as JSON
        log.SetFormatter(&log.JSONFormatter{})
        
        // send output to file
        log.SetOutput(logFp)
    }