How is automatic cleanup of unnecessary data in memory implemented in programming languages?

In programming languages such as Go, automatic memory management is implemented using a garbage collector (GC). The garbage collector tracks objects in memory and determines which ones are no longer used by the program (i.e., have no references). Such objects are considered "garbage" and are automatically freed to prevent memory leaks.

In Go, the garbage collector runs concurrently with the program execution, periodically pausing it briefly to analyze and clean up unused objects. This allows developers not to worry about manually freeing memory, as in languages with manual memory management.

Example:

package main

import "fmt"

func main() {
    data := make([]int, 1000000) // allocate memory
    fmt.Println(len(data))
    // After exiting main, if there are no references to data, the memory will be automatically freed by the garbage collector
}