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Go Channel

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My notes about Go channel.

Channels are a typed conduit through which you can send and receive values with the channel operator, <-.

  • Channel can only save homogeneous data type. So you must declare the type of the channel you want to create.

    chan int // channel only accepts int
    chan string // channel only accepts string
    chan bool // channel only accepts bool
    
    chan int // channel only accepts int
    chan string // channel only accepts string
    chan bool // channel only accepts bool
    
  • You need to initialize a channel before using it with make, otherwise the channel is nil and not available to use.

    // Syntax: {variable_name} := make(chan {type})
    ch := make(chan int) // works
    var ch2 chan int // don't work
    
    // Syntax: {variable_name} := make(chan {type})
    ch := make(chan int) // works
    var ch2 chan int // don't work
    
  • You need to initialize a channel before using it with make.

    ch := make(chan int) // int is type of channel data
    
    ch := make(chan int) // int is type of channel data
    
  • Sending/Receiving data using channel:

    x := <- ch // read data from channel ch into variable x
    ch <- y // send y to the channel ch
    
    x := <- ch // read data from channel ch into variable x
    ch <- y // send y to the channel ch
    
  • Close a channel:

    close(ch)
    
    close(ch)
    

    Note: You cannot send data to a closed channel.

  • Type of channels:

    • unbuffered channel: a channel is created with no capacity.
      // Syntax: {variable_name} := make(chan {type})
      ch := make(chan int) // unbuffered channel
      
      // Syntax: {variable_name} := make(chan {type})
      ch := make(chan int) // unbuffered channel
      
    • buffered channel: a channel is created with capacity.
      // Syntax: {variable_name} := make(chan {type}, {capacity})
      ch := make(chan int, 5) // buffered channel, capacity = 5
      
      // Syntax: {variable_name} := make(chan {type}, {capacity})
      ch := make(chan int, 5) // buffered channel, capacity = 5
      
  • Channel blocking mechanism:

    • Unbuffered channel

      Sending and receiving are blocked until the other side is ready. This allows goroutines to synchronize without explicit locks or condition variables.

      ch := make(chan int) // unbuffered channel
      
      ch := make(chan int) // unbuffered channel
      
    • Buffered channel

      Sending data to a buffered channel are blocked only when the buffer is full.

      Receiving data from a buffered channel are blocked only when the buffer is empty.

      ch := make(chan int, 5) // buffered channel
      
      ch := make(chan int, 5) // buffered channel
      
  • Deadlock with channel

    A deadlock happens when a group of goroutines are waiting for each other and none of them is able to proceed. Examples:

    • The data which are sent into a channel cannot be received by any receiver anywhere in your code.
    • You try to read data from a channel but there is no data are sent to the channel anywhere in your code.