long lived resolver crashes randomly, fix included

[quintilation]

Hi,

I am using a long lived resolver which sometimes generates "write on closed channel" panics.

The fix below just copies the pattern from the stopProbing channel:

diff --git a/service.go b/service.go
index 6253c54..42ab5bd 100644
--- a/service.go
+++ b/service.go
@@ -72,7 +72,8 @@ type lookupParams struct {

isBrowsing  bool
stopProbing chan struct{}

• once sync.Once

• noMore sync.Once
• stop sync.Once
  }

// newLookupParams constructs a lookupParams.
@@ -91,11 +92,11 @@ func newLookupParams(instance, service, domain string, isBrowsing bool, entries
// Notify subscriber that no more entries will arrive. Mostly caused
// by an expired context.
func (l *lookupParams) done() {

• close(l.Entries)

• l.noMore.Do(func() { close(l.Entries) })
  }

func (l *lookupParams) disableProbing() {

• l.once.Do(func() { close(l.stopProbing) })

• l.stop.Do(func() { close(l.stopProbing) })
  }

// ServiceEntry represents a browse/lookup result for client API.