ghetzel/pivot: dal/collection.go; 20 LoC

Found a possible issue in [ghetzel/pivot](https://www.github.com/ghetzel/pivot) at [dal/collection.go](https://github.com/ghetzel/pivot/blob/16cfffa66b04b0c4070ec04cbe79659ccb7d28a5/dal/collection.go#L793-L812)

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.

> reference to myField was used in a composite literal at line 809

[Click here to see the code in its original context.](https://github.com/ghetzel/pivot/blob/16cfffa66b04b0c4070ec04cbe79659ccb7d28a5/dal/collection.go#L793-L812)

Click here to show the 20 line(s) of Go which triggered the analyzer.

```go
for _, myField := range self.Fields {
if theirField, ok := actual.GetField(myField.Name); ok {
if diff := myField.Diff(&theirField); diff != nil {
for i, _ := range diff {
diff[i].Collection = self.Name
}

differences = append(differences, diff...)
}
} else {
differences = append(differences, &SchemaDelta{
Type: FieldDelta,
Issue: FieldMissingIssue,
Message: `is missing`,
Collection: self.Name,
Name: myField.Name,
ReferenceField: &myField,
})
}
}

```

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: 16cfffa66b04b0c4070ec04cbe79659ccb7d28a5

Start with dal/collection.go lines 793-812 at commit 16cfffa66b04b0c4070ec04cbe79659ccb7d28a5 and review the range-loop pointer finding in its Go context. Decide whether referencing myField in ReferenceField is a bug, mitigated, or desirable behavior, then leave the corresponding reaction on the issue.

Written by the indexing model from the issue text.