How to stop a goroutine

Question

I have a goroutine that calls a method  and passes returned value on a channel   ch    make chan int  100  go func        for           ch  lt - do stuff               How do I stop such a goroutine

User · Answer

Typically  you pass the goroutine a  possibly separate  signal channel  That signal channel is used to push a value into when you want the goroutine to stop  The goroutine polls that channel regularly  As soon as it detects a signal  it quits   quit    make chan bool  go func         for           select           case  lt - quit              return         default                 Do other stuff                         Do stuff     Quit goroutine quit  lt - true

User · Answer

Generally  you could create a channel and receive a stop signal in the goroutine   There two way to create channel in this example    channel context  In the example I will demo context WithCancel   The first demo  use channel   package main  import  fmt  import  time   func do stuff   int       return 1    func main          ch    make chan int  100      done    make chan struct        go func             for               select               case ch  lt - do stuff                case  lt -done                  close ch                  return                           time Sleep 100   time Millisecond                         go func             time Sleep 3   time Second          done  lt - struct                  for i    range ch           fmt Println  receive value     i             fmt Println  finish       The second demo  use context   package main  import        context       fmt       time     func main         forever    make chan struct        ctx  cancel    context WithCancel context Background         go func ctx context Context            for               select               case  lt -ctx Done        if cancel   execute                 forever  lt - struct                     return             default                  fmt Println  for loop                              time Sleep 500   time Millisecond                  ctx       go func             time Sleep 3   time Second          cancel                 lt -forever     fmt Println  finish

User · Answer

You can t kill a goroutine from outside  You can signal a goroutine to stop using a channel  but there s no handle on goroutines to do any sort of meta management  Goroutines are intended to cooperatively solve problems  so killing one that is misbehaving would almost never be an adequate response  If you want isolation for robustness  you probably want a process

User · Answer

I know this answer has already been accepted  but I thought I d throw my 2cents in  I like to use the tomb package  It s basically a suped up quit channel  but it does nice things like pass back any errors as well  The routine under control still has the responsibility of checking for remote kill signals  Afaik it s not possible to get an  id  of a goroutine and kill it if it s misbehaving  ie  stuck in an infinite loop    Here s a simple example which I tested   package main  import      launchpad net tomb     time     fmt     type Proc struct     Tomb tomb Tomb    func  proc  Proc  Exec       defer proc Tomb Done      Must call only once   for       select       case  lt -proc Tomb Dying          return     default        time Sleep 300   time Millisecond        fmt Println  Loop the loop                func main       proc     amp Proc     go proc Exec     time Sleep 1   time Second    proc Tomb Kill fmt Errorf  Death from above      err    proc Tomb Wait      Will return the error that killed the proc   fmt Println err      The output should look like     Loop the loop   Loop the loop   Loop the loop   Loop the loop   Death from above

User · Answer

EDIT  I wrote this answer up in haste  before realizing that your question is about sending values to a chan inside a goroutine   The approach below can be used either with an additional chan as suggested above  or using the fact that the chan you have already is bi-directional  you can use just the one     If your goroutine exists solely to process the items coming out of the chan  you can make use of the  close  builtin and the special receive form for channels   That is  once you re done sending items on the chan  you close it   Then inside your goroutine you get an extra parameter to the receive operator that shows whether the channel has been closed   Here is a complete example  the waitgroup is used to make sure that the process continues until the goroutine completes    package main  import  sync  func main         var wg sync WaitGroup     wg Add 1       ch    make chan int      go func             for               foo  ok     lt - ch             if  ok                   println  done                   wg Done                   return                           println foo                        ch  lt - 1     ch  lt - 2     ch  lt - 3     close ch       wg Wait

User · Answer

Personally  I d like to use range on a channel in a goroutine  https   play golang org p qt48vvDu8cd package main  import        quot fmt quot       quot sync quot     func main         var wg sync WaitGroup     c    make chan bool      wg Add 1      go func             defer wg Done           for b    range c               fmt Printf  quot Hello  t n quot   b                        c  lt - true     c  lt - true     close c      wg Wait      Dave has written a great post about this  http   dave cheney net 2013 04 30 curious-channels

[go] How to stop a goroutine

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