Accept net.OpErrors in this test, too

If a connection.close operation fails before the connection is marked
as closed internally, it's still a reasonable error for Connection#Close to return.

Note that it only happens with a certain degree of concurrency
in this test and thus the occurrence is quite unlikely in practice.

References #227.

connection_test.go

@@ -2,6 +2,7 @@ package amqp
 
 import (
  "log"
+ "net"
  "sync"
  "testing"
 )
@@ -48,13 +49,22 @@ func TestConcurrentClose(t *testing.T) {
  log.Fatalf("Could't connect to amqp server, err = %s", err)
  }
 
+ n := 32
  wg := sync.WaitGroup{}
- wg.Add(5)
- for i := 0; i < 5; i++ {
+ wg.Add(n)
+ for i := 0; i < n; i++ {
  go func() {
  err := conn.Close()
  if err != nil && err != ErrClosed {
- log.Fatalf("Expected nil or ErrClosed - got %#v, type is %T", err, err)
+ switch err.(type) {
+ case *Error:
+ log.Fatalf("Expected no error, or ErrClosed, or a net.OpError from conn.Close(), got %#v (%#v) of type %T", err, err.Error(), err)
+ case *net.OpError:
+ // this is acceptable: we got a net.OpError
+ // before the connection was marked as closed
+ break;
+ }
+
  }
  wg.Done()
  }()