Close of Nil Channel

Why This Happens

Closing a nil channel causes a panic. This typically happens when a channel variable is declared but never initialized with make(), or when a function returns a nil channel under certain conditions.

The Problem

func main() {
    var ch chan int
    close(ch) // panic: close of nil channel
}

The Fix

func main() {
    ch := make(chan int)
    close(ch)
}

Step-by-Step Fix

1. 1

   Identify the nil channel

   Find the close() call and check if the channel variable could be nil.

2. 2

   Trace initialization

   Follow the channel variable back to see if make() was called on it.

3. 3

   Add nil check or initialize

   Either ensure the channel is always initialized, or add a nil check before closing.