Channels Cheatsheet

Goroutines

• Spawn: go funcName()
• Anonymous: go func() { ... }()

Channels

• Create (Unbuffered): ch := make(chan int)
• Create (Buffered): ch := make(chan int, 100)
• Send: ch <- value
• Receive: v := <-ch
• Signalling: ch := make(chan struct{})

Closing & Safety

• Close: close(ch)
• Check: v, ok := <-ch (ok is false if empty and closed)
• Rules:
  • Sending to closed channel → Panic
  • Closing already closed channel → Panic
  • Receiving from closed channel → Zero value

Iteration & Selection

• Range: for v := range ch { ... } (exits when closed)
• Select:

select {
case v := <-ch1:
case ch2 <- 42:
default: // Makes select non-blocking
}

Time & Direction

• Ticker: time.Tick(1 * time.Second)
• Timeout: time.After(5 * time.Second)
• Read-Only: <-chan T
• Write-Only: chan<- T

Critical Notes

• Nil channels block forever (send or receive).
• Slices and maps are reference types; channels are too.
• If main exits, all other goroutines die immediately.