Aliased slices should be consistent with builtin slices

In working with an API at work we had the use case on query params to accept the
following syntaxes:

- `?foo=1&foo=2&foo=3`
- `?foo=1,2,3`

Initially we were using only the former syntax, but then a new library was
developed that sent the latter syntax.  When we switched from defining our field
as `[]int` to a custom type `Ints` that implemented `UnmarshalParam` we found
that when there were multiple values for the same key, the `UnmarshalParam`
would only receive the first value and others would be lost.

This change brings
consistency between the builtin slices and the aliased slices for query
parameters.

bind.go

@@ -167,6 +167,7 @@ func (b *DefaultBinder) bindData(destination interface{}, data map[string][]stri
  return errors.New("binding element must be a struct")
  }
 
+LOOP:
  for i := 0; i < typ.NumField(); i++ {
  typeField := typ.Field(i)
  structField := val.Field(i)
@@ -217,11 +218,18 @@ func (b *DefaultBinder) bindData(destination interface{}, data map[string][]stri
  }
 
  // Call this first, in case we're dealing with an alias to an array type
- if ok, err := unmarshalField(typeField.Type.Kind(), inputValue[0], structField); ok {
- if err != nil {
- return err
+ for _, val := range inputValue {
+ if ok, err := unmarshalField(typeField.Type.Kind(), val, structField); ok {
+ if err != nil {
+ return err
+ }
+
+ // If we have one entry then we continue to the next field as to not
+ // overwrite the value.
+ if len(inputValue) == 1 {
+ continue LOOP
+ }
  }
- continue
  }
 
  numElems := len(inputValue)