title: Golang 1.5 io.Copy blocked with two TCPConn
body: <p><a href="http://play.golang.org/p/gZo5RqgY4F" rel="nofollow">http://play.golang.org/p/gZo5RqgY4F</a></p>
  
  <p>I have a question with <code>io.Copy</code> method. The link above will block in line 44 under Go 1.5. But will pass in 1.4.2. I have no idea with this issue.</p>
  
  <p>Here is my go version: <code>go version go 1.5 darwin/amd64</code>.</p>
  
  <p>When did the <code>io.Copy</code> return in go 1.5?</p>