fix(ConsoleSink): allow non async console logging

The async attribute was being set to true by default using the or construct, making it impossible to pass false as value. Add missing test.

lua/structlog/sinks/console.lua

@@ -16,7 +16,7 @@ setmetatable(Console, {
 
 function Console:new(async)
   local console = {
-    async = async or true,
+    async = async,
   }
 
   Console.__index = Console

test/unit/sinks/console_spec.lua

@@ -0,0 +1,21 @@
+local log = require("structlog")
+local Console = log.sinks.Console
+
+local stub = require("luassert.stub")
+
+describe("Console constructor", function()
+  local handler = {}
+  stub(handler, "handle")
+
+  it("should create an async console logger", function()
+    local sink = Console(true)
+
+    assert.True(sink.async)
+  end)
+
+  it("should create an non-async console logger", function()
+    local sink = Console(false)
+
+    assert.False(sink.async)
+  end)
+end)