std specs: use isolate execution context instead of bare thread

spec/std/execution_context/global_queue_spec.cr

@@ -1,6 +1,7 @@
 {% skip_file if flag?(:interpreted) %}
 
 require "./spec_helper"
+require "../../support/thread"
 
 describe ExecutionContext::GlobalQueue do
   it "#initialize" do
@@ -99,10 +100,10 @@ describe ExecutionContext::GlobalQueue do
       increments = 15
       queue = ExecutionContext::GlobalQueue.new(Thread::Mutex.new)
       ready = Thread::WaitGroup.new(n)
-      shutdown = Thread::WaitGroup.new(n)
+      threads = Array(Thread).new(n)
 
       n.times do |i|
-        Thread.new(name: "ONE-#{i}") do |thread|
+        threads << new_thread(name: "ONE-#{i}") do
           slept = 0
           ready.done
 
@@ -118,10 +119,6 @@ describe ExecutionContext::GlobalQueue do
               break
             end
           end
-        rescue exception
-          Crystal::System.print_error "\nthread: #{thread.name}: exception: #{exception}"
-        ensure
-          shutdown.done
         end
       end
       ready.wait
@@ -131,7 +128,7 @@ describe ExecutionContext::GlobalQueue do
         Thread.sleep(10.nanoseconds) if i % 10 == 9
       end
 
-      shutdown.wait
+      threads.each(&.join)
 
       # must have dequeued each fiber exactly X times
       fibers.each { |fc| fc.counter.should eq(increments) }
@@ -147,10 +144,10 @@ describe ExecutionContext::GlobalQueue do
 
       queue = ExecutionContext::GlobalQueue.new(Thread::Mutex.new)
       ready = Thread::WaitGroup.new(n)
-      shutdown = Thread::WaitGroup.new(n)
+      threads = Array(Thread).new(n)
 
       n.times do |i|
-        Thread.new(name: "BULK-#{i}") do |thread|
+        threads << new_thread("BULK-#{i}") do
           slept = 0
 
           r = ExecutionContext::Runnables(3).new(queue)
@@ -201,10 +198,6 @@ describe ExecutionContext::GlobalQueue do
             slept += 1
             Thread.sleep(1.nanosecond) # don't burn CPU
           end
-        rescue exception
-          Crystal::System.print_error "\nthread #{thread.name} raised: #{exception}"
-        ensure
-          shutdown.done
         end
       end
       ready.wait
@@ -217,7 +210,7 @@ describe ExecutionContext::GlobalQueue do
         Thread.sleep(10.nanoseconds) if i % 4 == 3
       end
 
-      shutdown.wait
+      threads.each(&.join)
 
       # must have dequeued each fiber exactly X times (no less, no more)
       fibers.each { |fc| fc.counter.should eq(increments) }