func (f *DurationFlag) Names() []string {
	return flagNames(f.Name, f.Aliases)
}
Names returns the names of the flag
package cli
import (
	"flag"
	"fmt"
	"time"
)
type DurationFlag struct {
	Name        string
	Aliases     []string
	Usage       string
	EnvVars     []string
	FilePath    string
	Required    bool
	Hidden      bool
	Value       time.Duration
	DefaultText string
	Destination *time.Duration
	HasBeenSet  bool
}
func (f *DurationFlag) IsSet() bool {
	return f.HasBeenSet
}
func (f *DurationFlag) String() string {
	return FlagStringer(f)
}