Reduce CPU load

`Fiber.yield` sleeps for 0 seconds. When used in a loop, this,
effectively, maxes out CPU if there are no other resumable fibers.

CHANGELOG.md

@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased] - 
+
+### Fixed
+- Replace `Fiber.yield` with `sleep 1.microsecond` in loops to reduce CPU load
+
 ## [0.18.0] - 2023-12-07
 
 ### Changed

spec/mel_spec.cr

@@ -24,7 +24,7 @@ describe Mel do
 
       100_000.times do
         break if Mel.state.stopped?
-        Fiber.yield
+        sleep 1.microsecond
       end
 
       Mel.state.stopped?.should be_true
@@ -39,7 +39,7 @@ describe Mel do
 
       100_000.times do
         break if Mel.state.stopped?
-        Fiber.yield
+        sleep 1.microsecond
       end
 
       Mel.state.stopped?.should be_true

src/worker.cr

@@ -34,7 +34,7 @@ module Mel
     spawn { start }
 
     until state.started?
-      Fiber.yield
+      sleep 1.microsecond
     end
   end
 
@@ -55,7 +55,7 @@ module Mel
     lock { @@state = State::Stopping } unless state.stopped?
 
     until state.stopped?
-      Fiber.yield
+      sleep 1.microsecond
     end
   end