如下

go
package colour

type Colour int
const (
   Red Colour = iota
   Green
   Blue
)

func (c Colour) String() string
{
switch c {
case Red:
     return "Red"
case Green:
     return "Green"
case Blue:
     return "Blue"
default:
     panic("unknown colour")
}
}

// 其他包导入

import "example/colour"

var c Colour= colour.Red
fmt.Println(c)

参考：

https://mp.weixin.qq.com/s/m2N6YSEqseRfrqLjDWZIZQ

https://mp.weixin.qq.com/s/f4U4VVYBifi78JQC6D8KuA