stream.Wait() panic when callback is nil

[rhyshmwang]

func Wait will panic, because callback is nil.

Can func Wait support nil callback? Maybe do nothing when callback is nil is better

st := stream.New().WithMaxGoroutines(20)

st.Go(func() stream.Callback {
    return nil
}

st.Wait()

[rhyshmwang]

There is an example. Recover() in st.Go works, but st.Wait() still panic.

package main
import (
    "fmt"
    "github.com/sourcegraph/conc/stream"
    "time"
)
func main() {
    for i := 0; i < 5; i++ {
       st := stream.New().WithMaxGoroutines(20)
       for i := 0; i < 10; i++ {
          idx := i
          st.Go(func() (callback stream.Callback) {
             //callback = func() {} // if comment will panic
             defer func() {
                if err := recover(); err != nil {
                   fmt.Println("haha", err)
                }
             }()
             if idx == 2 || idx == 4 {
                panic(idx) // this panic will be recovered
             }
             return func() {
             }
          })
       }
       st.Wait() // panic occurs here
    }
    time.Sleep(1 * time.Second)
}