go-concurrency

Aims to learn the knowledge about concurrency in Go

Flow control with channels

1. We can imagine that channel is a pipe, chan<- means to send a value into the channel. <-chan means to receive a value from the channel.

2. select ... case can execute sending value into a channel

Range and Close

1. A sender can close a channel to indicate that no more values will be sent.
2. Receivers can test whether a channel has been closed by assigning a second parameter to the receive expression. v, ok := <-ch, ok is false if there are no more values to receive and the channel is closed.
3. The loop for i:= range c receives values from the channel repeatedly until it is closed.
4. Only the sender should close a channel, never the receiver. Sending on a closed channel will cause a panic.
5. Channels aren't like files; you don't usually need to close them. Closing is only necessary when the receiver must be told there are no more values coming, such as to terminate a range loop.

Select

1. The select statement lets a goroutine wait on multiple communication operations
2. A select blocks until one of its cases can run, then it executes that case. It chooses one at random if multiple are ready

Default selection

1. The default case in a select is run if no other case is ready.
2. Use a default case to try a send or receive without blocking

select {
    case i:= <-c:
        // use i
    default: 
        // receive when c is blocked        
}