fasthttputil: add errInmemoryListenerClosed (#678)

* add errInmemoryListenerClosed

* Fix test error

* Expose ErrInmemoryListenerClosed

* rename

1 files changed, 6 insertions, 4 deletions

diff --git a/fasthttputil/inmemory_listener.go b/fasthttputil/inmemory_listener.go
index 1b1a5f3..fd41fc8 100644
--- a/fasthttputil/inmemory_listener.go
+++ b/fasthttputil/inmemory_listener.go
@@ -1,11 +1,13 @@
 package fasthttputil
 
 import (
-	"fmt"
+	"errors"
 	"net"
 	"sync"
 )
 
+var ErrInmemoryListenerClosed = errors.New("InmemoryListener is already closed: use of closed network connection")
+
 // InmemoryListener provides in-memory dialer<->net.Listener implementation.
 //
 // It may be used either for fast in-process client<->server communications
@@ -36,7 +38,7 @@ func NewInmemoryListener() *InmemoryListener {
 func (ln *InmemoryListener) Accept() (net.Conn, error) {
 	c, ok := <-ln.conns
 	if !ok {
-		return nil, fmt.Errorf("InmemoryListener is already closed: use of closed network connection")
+		return nil, ErrInmemoryListenerClosed
 	}
 	close(c.accepted)
 	return c.conn, nil
@@ -51,7 +53,7 @@ func (ln *InmemoryListener) Close() error {
 		close(ln.conns)
 		ln.closed = true
 	} else {
-		err = fmt.Errorf("InmemoryListener is already closed")
+		err = ErrInmemoryListenerClosed
 	}
 	ln.lock.Unlock()
 	return err
@@ -88,7 +90,7 @@ func (ln *InmemoryListener) Dial() (net.Conn, error) {
 	ln.lock.Unlock()
 
 	if cConn == nil {
-		return nil, fmt.Errorf("InmemoryListener is already closed")
+		return nil, ErrInmemoryListenerClosed
 	}
 	return cConn, nil
 }