Shared memory versus message passing

If you have been developing with Go for some time, you have probably heard the phrase “Do not communicate by sharing memory. Instead, share memory by communicating.” Sharing memory among the concurrent blocks of a program creates vast opportunities for subtle bugs that are hard to diagnose. These problems manifest themselves randomly, usually under load that cannot be simulated in a controlled test environment, and they are hard or impossible to reproduce. What cannot be reproduced cannot be tested, so finding such problems is usually a matter of luck. Once found, they are usually easy to fix with very minor changes. That adds insult to injury. Go supports both shared memory and message-passing models, so we will spend some time looking at what the shared memory and message-passing paradigms are.

In a shared memory system, there can be multiple processors or cores with multiple execution threads that use the same memory. In a Uniform...