dictionary in Go

```
package main
import "fmt"

func main() {
    m := make(map[int]int)
    m[1] = 1
    m[2] = 2
    m[3] = 3
    
    delete(m, 1)
    
    if v, ok := m[2]; ok {
        fmt.Println(v)
    }
    
    for k, v := range m {
        fmt.Print(k, ":", v, "\n")
    }
}
```