Support older rubies.

lib/async/scheduler.rb

@@ -165,15 +165,28 @@ def address_resolve(hostname)
 			::Resolv.getaddresses(hostname)
 		end
 
+
+		if IO.method_defined?(:timeout)
+			private def get_timeout(io)
+				io.timeout
+			end
+		else
+			private def get_timeout(io)
+				nil
+			end
+		end
+
 		# @asynchronous May be non-blocking..
 		def io_wait(io, events, timeout = nil)
 			fiber = Fiber.current
 
 			if timeout
+				# If an explicit timeout is specified, we expect that the user will handle it themselves:
 				timer = @timers.after(timeout) do
 					fiber.transfer
 				end
-			elsif timeout = io.timeout
+			elsif timeout = get_timeout(io)
+				# Otherwise, if we default to the io's timeout, we raise an exception:
 				timer = @timers.after(timeout) do
 					fiber.raise(::IO::TimeoutError, "Timeout while waiting for IO to become ready!")
 				end
@@ -183,12 +196,12 @@ def io_wait(io, events, timeout = nil)
 		ensure
 			timer&.cancel
 		end
-
+		
 		if ::IO::Event::Support.buffer?
 			def io_read(io, buffer, length, offset = 0)
 				fiber = Fiber.current
 
-				if timeout = io.timeout
+				if timeout = get_timeout(io)
 					timer = @timers.after(timeout) do
 						fiber.raise(::IO::TimeoutError, "execution expired")
 					end
@@ -203,7 +216,7 @@ def io_read(io, buffer, length, offset = 0)
 				def io_write(io, buffer, length, offset = 0)
 					fiber = Fiber.current
 
-					if timeout = io.timeout
+					if timeout = get_timeout(io)
 						timer = @timers.after(timeout) do
 							fiber.raise(::IO::TimeoutError, "execution expired")
 						end