Add linter structcheck (#537)

.golangci.yml

@@ -18,7 +18,9 @@ linters:
     - misspell
     - whitespace
     - staticcheck
+    - structcheck
     - varcheck
+
 run:
   timeout: 5m
 

server/logging/log.go

@@ -31,7 +31,6 @@ type stream struct {
 	list []*Entry
 	subs map[*subscriber]struct{}
 	done chan struct{}
-	wait sync.WaitGroup
 }
 
 type log struct {

server/queue/fifo.go

@@ -21,7 +21,6 @@ const (
 type entry struct {
 	item     *Task
 	done     chan bool
-	retry    int
 	error    error
 	deadline time.Time
 }