为什么计数器不通过方法增加函数参数

I try writing simple counter but I don't understand why he didn't work.. There is my code

package main

import "fmt"

type Count int

type Counter interface {
    Next()
    Prev()
    Jump(j int) //i want increase Count to 'j' value
}

func (c *Count) Next() { *c += 1 }
func (c *Count) Prev() { *c -= 1 }
func (c *Count) Jump(j int) { *c += j } //Here Error

func main() {
    val := new(Count) //0
    val.Next() //+1
    val.Jump(4) //+4
    val.Prev() //-1
    fmt.Println("Now ", *val) //expected 4
}

Is anybody knows what the problem here? Thanks for advance!

Simply change the Jump signature:

Jump(j Count)

And you will get the expected result.

See play.golang.org

If you don't, you would get:

prog.go:15: invalid operation: *c += j (mismatched types Count and int)
 [process exited with non-zero status]