ax(mining): rename wg to waitGroup in circuit breaker concurrency test

AX Principle 1: predictable names over short names. wg requires
mental mapping to WaitGroup; waitGroup is self-documenting.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/circuit_breaker_test.go

@@ -302,11 +302,11 @@ func TestCircuitBreaker_Reset_Good(t *testing.T) {
 func TestCircuitBreaker_Concurrency_Ugly(t *testing.T) {
 	cb := NewCircuitBreaker("test", DefaultCircuitBreakerConfig())
 
-	var wg sync.WaitGroup
+	var waitGroup sync.WaitGroup
 	for i := 0; i < 100; i++ {
-		wg.Add(1)
+		waitGroup.Add(1)
 		go func(n int) {
-			defer wg.Done()
+			defer waitGroup.Done()
 			cb.Execute(func() (interface{}, error) { //nolint:errcheck
 				if n%3 == 0 {
 					return nil, errors.New("fail")
@@ -315,7 +315,7 @@ func TestCircuitBreaker_Concurrency_Ugly(t *testing.T) {
 			})
 		}(i)
 	}
-	wg.Wait()
+	waitGroup.Wait()
 
 	_ = cb.State()
 }