gophergala2016/supbot: Godeps/_workspace/src/github.com/pressly/sup/sup.go; 83 LoC

Found a possible issue in [gophergala2016/supbot](https://www.github.com/gophergala2016/supbot) at [Godeps/_workspace/src/github.com/pressly/sup/sup.go](https://github.com/gophergala2016/supbot/blob/77bb0a281f3b453a5db003414b38bf28f8bed613/Godeps/_workspace/src/github.com/pressly/sup/sup.go#L104-L186)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first issue it finds, so please do not limit your consideration to the contents of the below message.

> range-loop variable task used in defer or goroutine at line 149

[Click here to see the code in its original context.](https://github.com/gophergala2016/supbot/blob/77bb0a281f3b453a5db003414b38bf28f8bed613/Godeps/_workspace/src/github.com/pressly/sup/sup.go#L104-L186)

Click here to show the 83 line(s) of Go which triggered the analyzer.

```go
for _, task := range tasks {
var writers []io.Writer
var wg sync.WaitGroup

// Run tasks on the provided clients.
for _, c := range task.Clients {
prefix, prefixLen := c.Prefix()
if len(prefix) < maxLen { // Left padding.
prefix = strings.Repeat(" ", maxLen-prefixLen) + prefix
}

err := c.Run(task)
if err != nil {
return fmt.Errorf("%s%v", prefix, err)
}

// Copy over tasks's STDOUT.
wg.Add(1)
go func(c Client) {
defer wg.Done()
_, err := io.Copy(os.Stdout, prefixer.New(c.Stdout(), prefix))
if err != nil && err != io.EOF {
// TODO: io.Copy() should not return io.EOF at all.
// Upstream bug? Or prefixer.WriteTo() bug?
fmt.Fprintf(os.Stderr, "%sSTDOUT: %v", prefix, err)
}
}(c)

// Copy over tasks's STDERR.
wg.Add(1)
go func(c Client) {
defer wg.Done()
_, err := io.Copy(os.Stderr, prefixer.New(c.Stderr(), prefix))
if err != nil && err != io.EOF {
fmt.Fprintf(os.Stderr, "%sSTDERR: %v", prefix, err)
}
}(c)

writers = append(writers, c.Stdin())
}

// Copy over task's STDIN.
if task.Input != nil {
go func() {
writer := io.MultiWriter(writers...)
_, err := io.Copy(writer, task.Input)
if err != nil && err != io.EOF {
fmt.Fprintf(os.Stderr, "STDIN: %v", err)
}
// TODO: Use MultiWriteCloser (not in Stdlib), so we can writer.Close() instead?
for _, c := range clients {
c.WriteClose()
}
}()
}

// Wait for all I/O operations first.
wg.Wait()

// Make sure each client finishes the task, return on failure.
for _, c := range task.Clients {
wg.Add(1)
go func(c Client) {
defer wg.Done()
if err := c.Wait(); err != nil {
prefix, prefixLen := c.Prefix()
if len(prefix) < maxLen { // Left padding.
prefix = strings.Repeat(" ", maxLen-prefixLen) + prefix
}
if e, ok := err.(*ssh.ExitError); ok && e.ExitStatus() != 15 {
// TODO: Store all the errors, and print them after Wait().
fmt.Fprintf(os.Stderr, "%sexit %v\n", prefix, e.ExitStatus())
os.Exit(e.ExitStatus())
}
fmt.Fprintf(os.Stderr, "%s%v\n", prefix, err)
os.Exit(1)
}
}(c)
}

// Wait for all commands to finish.
wg.Wait()
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 77bb0a281f3b453a5db003414b38bf28f8bed613

Start in Godeps/_workspace/src/github.com/pressly/sup/sup.go around lines 104-186, especially the task range and goroutines near line 149. Trace how the range variables are used by deferred or concurrent work and compare that with the analyzer warning; done means the reported capture issue is addressed without changing the task execution behavior.

Written by the indexing model from the issue text.