Threading Goroutines in Go: Running a Constant Number Simultaneously

The realm of Go concurrency offers a plethora of materials on awaiting the completion of a specified number of goroutines. However, a distinct challenge presents itself: ensuring a continuous execution of a predefined number of goroutines, with one commencing as another concludes.

Consider a scenario with a substantial quantity of tasks, such as processing data retrieved from a MySQL database. A naive approach might initiate a vast number of parallel goroutines, simultaneously executing hundreds of thousands of tasks. In contrast, the desired behavior limits the concurrently running goroutines to a fixed count (say, 20).

This controlled concurrency pattern is known as "bounded parallelism." Implementing this pattern in Go entails employing a channel of empty structs as a semaphore, dictating the maximum number of concurrent worker goroutines. Here's an illustration:

package main

import "fmt"

func main() {
    maxGoroutines := 10
    guard := make(chan struct{}, maxGoroutines)

    for i := 0; i 
This implementation ensures that no more than the specified number of goroutines execute concurrently. As a result, when a worker goroutine finishes, a new goroutine is immediately launched, maintaining the desired concurrency level.
The "Go Concurrency Patterns" article further explores this concept in its "Bounded parallelism" section, providing deeper insights into this crucial concurrency technique.