sourcegraph/go-langserver: pkg/tools/buildutil.go; 21 LoC

Found a possible issue in [sourcegraph/go-langserver](https://www.github.com/sourcegraph/go-langserver) at [pkg/tools/buildutil.go](https://github.com/sourcegraph/go-langserver/blob/4b49d01c8a692968252730d45980091dcec7752e/pkg/tools/buildutil.go#L29-L49)

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 root used in defer or goroutine at line 45

[Click here to see the code in its original context.](https://github.com/sourcegraph/go-langserver/blob/4b49d01c8a692968252730d45980091dcec7752e/pkg/tools/buildutil.go#L29-L49)

Click here to show the 21 line(s) of Go which triggered the analyzer.

```go
for _, root := range ctxt.SrcDirs() {
root = path.Clean(root)

if util.PathHasPrefix(root, dir) {
// If we are a child of dir, we can just start at the
// root. A concrete example of this happening is when
// root=/goroot/src and dir=/goroot
dir = root
}

if !util.PathHasPrefix(dir, root) {
continue
}

wg.Add(1)
go func() {
allPackages(ctxt, root, dir, ch)
wg.Done()
}()
dirInGOPATH = true
}

```

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See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 4b49d01c8a692968252730d45980091dcec7752e