I have this which I have faith is close to working as desired. What I am trying to do is range over a sequence, but be able to call the next item yourself and asynchronously

sync:

for r := range even.Sequence() {
    if !r.Done {
        r.Contnue()
    }
}

or async:

   for r := range even.Sequence() {
        go func(){
          if !r.Done {
            r.Contnue()
           }
        }()
    }

here is the full code in main:

package main

import "fmt"

type HasNext[T any] interface {
    Next() (bool, T)
}

type Nexter[T int] struct {
    Val int
    End int
}

type Ret struct {
    Done    bool
    Value   int
    Contnue func()
}

func (n *Nexter[int]) Sequence() chan Ret {

    var c = make(chan Ret)
    even := newEven()

    var x func()

    x = func() {
        fmt.Println("got here 3")
        <-c
        fmt.Println("got here 4")
        fmt.Println("got here 5")
        var b, v = even.Next()
        c <- Ret{b, v, x}
        if b {
            close(c)
        }
    }

    go func() {
        var b, v = even.Next()
        fmt.Println("got here 1")
        c <- Ret{b, v, x}
        fmt.Println("got here 2")
    }()

    return c

}

func (n *Nexter[int]) Next() (bool, int) {
    n.Val = n.Val + 1
    if n.Val > n.End {
        return true, int(n.Val)
    }
    return false, int(n.Val)
}

func newEven() *Nexter[int] {
    n := 0
    return &Nexter[int]{n, 5}
}

func main() {


    even := newEven()


    for r := range even.Sequence() {

        fmt.Println("value:", r.Value)
        if !r.Done {
            fmt.Println("continuing...")
            r.Contnue()
        }
    }

}

but currently I get this output:

```golang
got here 1
got here 2
value: 1
continuing…
got here 3
fatal error: all goroutines are asleep - deadlock!

goroutine 1 [chan receive]:
main.main()
/Users/me/codes/vibeirl/wss/test/iterator/main.go:83 +0x66
```

so clearly it’s deadlocking somewhere but not sure where/how exactly