Race Hazard in group.work()

[JoeReid]

The closure in the group.work() function in group.go has a race hazard sending to the channel inside the closure.
Link to code

For loops reuse the variables defined in their scope, meaning that the data available to a closure evoked in a go routine is not thread-safe.

Eg:

for ch, _ := range g.members {
            go func() 
                // ch not safe to use here
            }()
        }

Either taking a copy of the variable or passing it to the function as an argument would fix this errror.