Is(...) function

The Is(...) function allows you to pass one or multiple Validators, each with their respective values and rules for validation. This creates a Validation session, which can be used to validate multiple values.

In the following example, we pass multiple Validators for the full_name, age, and status values to the Is(...) function:

val := v.Is(
  v.String("Bob", "full_name").Not().Blank().OfLengthBetween(4, 20),
  v.Number(17, "age").GreaterThan(18),
  v.String("singl", "status").InSlice([]string{"married", "single"})
)

if !val.Valid() {
  out, _ := json.MarshalIndent(val.Error(), "", "  ")
  fmt.Println(string(out))
}
output:
```json
{
  "age": [
    "Age must be greater than \"18\""
  ],
  "full_name": [
    "Full name must have a length between \"4\" and \"20\""
  ],
  "status": [
    "Status is not valid"
  ]
}