golang: how to print data from running goroutine at fixed intervals?

Question

I'm having some trouble understanding channels in golang. As far as I know channels are the correct way to publish data to the console at a given time interval.

So say i have a goroutine that is doing work, and then in my main loop i would like to print data from that goroutine every second.

How would something like this be coded? A simple example would be greatly appreciated.

Answer 1

You can have some protected shared state in memory that you update from your long running process. Then you have a timer that triggers this shared state check every second. Here is a quick example: http://play.golang.org/p/gfGvhHUWIc

Code:

package main

import (
    "fmt"
    "sync"
    "time"
)

type Progress struct {
    current string
    rwlock  sync.RWMutex
}

func (p *Progress) Set(value string) {
    p.rwlock.Lock()
    defer p.rwlock.Unlock()
    p.current = value
}

func (p *Progress) Get() string {
    p.rwlock.RLock()
    defer p.rwlock.RUnlock()
    return p.current
}

func longJob(progress *Progress) {
    i := 0
    for {
        time.Sleep(100 * time.Millisecond)
        i++
        progress.Set(fmt.Sprintf("Current progress message: %v", i))
    }
}

func main() {
    fmt.Println("test")
    c := time.Tick(1 * time.Second)
    progress := &Progress{}
    go longJob(progress)
    for {
        select {
        case <-c:
            fmt.Println(progress.Get())
        }
    }
}