lib: Ensure timely service termination (fixes #5860) (#5863)

lib/beacon/beacon.go

@@ -8,7 +8,6 @@ package beacon
 
 import (
 	"net"
-	stdsync "sync"
 
 	"github.com/thejerf/suture"
 )
@@ -24,21 +23,3 @@ type Interface interface {
 	Recv() ([]byte, net.Addr)
 	Error() error
 }
-
-type errorHolder struct {
-	err error
-	mut stdsync.Mutex // uses stdlib sync as I want this to be trivially embeddable, and there is no risk of blocking
-}
-
-func (e *errorHolder) setError(err error) {
-	e.mut.Lock()
-	e.err = err
-	e.mut.Unlock()
-}
-
-func (e *errorHolder) Error() error {
-	e.mut.Lock()
-	err := e.err
-	e.mut.Unlock()
-	return err
-}