How Can Go Generics Be Used to Create Type-Safe Channels Handling Different Runtime Types?

Go Generic Container with Different Runtime Types

When it comes to sending data over a channel to a goroutine for further processing, the desire for a channel that can handle any type often arises. With the introduction of generics in Go 1.18, such a challenge appears manageable. However, there's a catch: specifying the channel's type to the goroutine upon initialization remains a hindrance since it can hold any data type.

In an attempt to address this issue, consider the following sample code:

type Message[T any] struct {
    Data T
}

type Packet[T any] struct {
    Msg Message[T]
}

func StartController[T any](sender chan Packet[T]) {
    go runThread(sender)
}

func runThread[T any](sender chan Packet[T]) {
    for true {
        data := <-sender
        fmt.Println(data)
    }
}

In this code, the StartController function begins a goroutine that executes the runThread function. However, there's a compilation error due to the attempt to use the generic type Packet[T interface{}] without instantiation.

A common misconception lies in using generics to create a channel that can accommodate any type. Similar to Java's List, a generic type must be instantiated with a concrete type parameter before it can be used, rendering the use of type parameters somewhat pointless.

To exemplify, consider Java's generic collector ArrayList. Its Go counterpart would be:

c := make(chan interface{})

In this case, the channel can accept any type of data. However, the question arises: how should the generic channel handle receive operations? If anything can be sent into it, what is the data type of the received item?

Therefore, the most suitable solution remains chan interface{} with type assertion upon receiving the item, as is done in the code without generics.

Instead, the true value of generics lies in writing code that handles arbitrary types while maintaining type safety. For instance:

func receiveAny[T any](c chan T) T {
    return <-c
}

This function can be called with either a chan int or a chan string.

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