Understanding goroutines

Question

I\'m trying to understand concurrency in Go. In particular, I wrote this thread-unsafe program:

package main

import          


        

Answer 1

There are a few things to keep in mind about Go's goroutines:

1. They are not threads in the sense of Java's or C++ threads
   • goroutines are more like greenlets
2. The go runtime multiplexes the goroutines across the system threads
   • the number of system threads is controlled by an environment variable GOMAXPROCS and defaults to 1 currently I think. This may change in the future
3. The way goroutines yield back to their current thread is controlled by several different constructs
   • the select statement can yield control back to the thread
   • sending on a channel can yield control back to the thread
   • doing IO operations can yield control back to the thread
   • runtime.Gosched() explicitly yields control back to the thread

The behavior you are seeing is because the main function never yields back to the thread and is instead involved in a busy loop and since there is only one thread the main loop has no place to run.