package main

import "fmt"
import "io"
import "log"
import "os"
import "strings"

var Log *log.Logger

type Job_Result struct {
    Job_ID int64
    // other stuff
    Log_Lines []string
}

// satisfies io.Writer interface
func (jr Job_Result) Write (p []byte) (n int, err error) {
    s := strings.TrimRight(string(p),"n ")
    jr.Log_Lines= append(jr.Log_Lines,s)
    return len(s), nil
}

func (jr Job_Result) Dump() {
    fmt.Println("nHere is a dump of the job result log lines:")
    for n, s := range jr.Log_Lines{
        fmt.Printf("tline %d: %sn",n,s)
    }
}

func main() {

    // make a Job_Result

    var jr Job_Result
    jr.Job_ID = 123
    jr.Log_Lines = make([]string,0)

    // create an io.MultiWriter that points to both stdout
    // and that Job_Result var

    var writers io.Writer
    writers = io.MultiWriter(os.Stdout,jr)

    Log = log.New(writers,
       "",
       log.Ldate|log.Ltime|log.Lshortfile)

    // send some stuff to the log

    Log.Println("program starting")
    Log.Println("something happened")
    Log.Printf("last thing that happened, should be %drd linen",3)

    jr.Dump()

}

2016/07/28 07:20:07 testjob.go:43: program starting
2016/07/28 07:20:07 testjob.go:44: something happened
2016/07/28 07:20:07 testjob.go:45: last thing that happened, should be 3rd line

Here is a dump of the job result log lines: