thoas/letitcrash: errors.go; 4 LoC

Found a possible issue in [thoas/letitcrash](https://www.github.com/thoas/letitcrash) at [errors.go](https://github.com/thoas/letitcrash/blob/4667f4369b87f9ad63d27e717f488bf8d349dc2b/errors.go#L27-L30)

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.

>

[Click here to see the code in its original context.](https://github.com/thoas/letitcrash/blob/4667f4369b87f9ad63d27e717f488bf8d349dc2b/errors.go#L27-L30)

Click here to show the 4 line(s) of Go which triggered the analyzer.

```go
for _, bucket := range buckets {
io.WriteString(out, p.BucketHeader(&bucket, fullPath, len(buckets) > 1))
io.WriteString(out, p.StackLines(&bucket.Signature, srcLen, pkgLen, fullPath))
}

```

Click here to show extra information the analyzer produced.

```
No path was found through the callgraph that could lead to a function which writes a pointer argument.

No path was found through the callgraph that could lead to a function which passes a pointer to third-party code.

root signature {BucketHeader 3} was not found in the callgraph; reference was passed directly to third-party code
```

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: 4667f4369b87f9ad63d27e717f488bf8d349dc2b

Start with errors.go lines 27-30 and inspect the reported range-loop pointer use in the linked commit. Read the analyzer output and the linked classification descriptions, then determine whether this instance is a Bug, Mitigated, or Desirable Behavior and leave the corresponding reaction.

Written by the indexing model from the issue text.