What is sync.Pool and what is it used for?

sync.Pool in Go is a data structure for storing and reusing temporary objects to reduce the load on the garbage collector and improve performance.

The main purpose is to cache objects that are frequently created and quickly become unnecessary, such as buffers or data structures. Instead of allocating memory each time, objects are taken from the pool and returned after use.

Example of usage:

var bufPool = sync.Pool{
    New: func() interface{} {
        return make([]byte, 1024) // create a new buffer of size 1KB
    },
}

func process() {
    buf := bufPool.Get().([]byte) // take a buffer from the pool
    defer bufPool.Put(buf)         // return the buffer back

    // use buf for operations
}

This helps reduce the number of allocations and improve performance in high-load applications.