code: func isTrue(val reflect.Value) (truth, ok bool) {
  	if !val.IsValid() {
  		// Something like var x interface{}, never set. It's a form of nil.
  		return false, true
  	}
  	switch val.Kind() {
  	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
  		truth = val.Len() > 0
  	case reflect.Bool:
  		truth = val.Bool()
  	case reflect.Complex64, reflect.Complex128:
  		truth = val.Complex() != 0
  	case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
  		truth = !val.IsNil()
  	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
  		truth = val.Int() != 0
  	case reflect.Float32, reflect.Float64:
  		truth = val.Float() != 0
  	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
  		truth = val.Uint() != 0
  	case reflect.Struct:
  		truth = true // Struct values are always true.
  	default:
  		return
  	}
  	return truth, true
  }
docs: // isTrue reports whether the value is 'true', in the sense of not the zero of its type,
  // and whether the value has a meaningful truth value.