add staticcheck linting (#3828)

cleanup to add linter

    grpc change:
        https://godoc.org/google.golang.org/grpc#WithContextDialer
        https://godoc.org/google.golang.org/grpc#WithDialer
        grpc/grpc-go#2627
    prometheous change:
        due to UninstrumentedHandler, being deprecated in the future
    empty branch = empty if or else statement
        didn't delete them entirely but commented
        couldn't find a reason to have them
    could not replicate the issue #3406
        but if want to keep it commented then we should comment out the if statement as well

libs/common/async.go

@@ -61,9 +61,10 @@ func (trs *TaskResultSet) Reap() *TaskResultSet {
 					TaskResult: result,
 					OK:         true,
 				}
-			} else {
-				// We already wrote it.
 			}
+			// else {
+			// We already wrote it.
+			// }
 		default:
 			// Do nothing.
 		}
@@ -83,9 +84,10 @@ func (trs *TaskResultSet) Wait() *TaskResultSet {
 				TaskResult: result,
 				OK:         true,
 			}
-		} else {
-			// We already wrote it.
 		}
+		// else {
+		// We already wrote it.
+		// }
 	}
 	return trs
 }

libs/common/async_test.go

@@ -40,9 +40,10 @@ func TestParallel(t *testing.T) {
 		} else if !assert.Equal(t, -1*i, taskResult.Value.(int)) {
 			assert.Fail(t, "Task should have returned %v but got %v", -1*i, taskResult.Value.(int))
 			failedTasks++
-		} else {
-			// Good!
 		}
+		// else {
+		// Good!
+		// }
 	}
 	assert.Equal(t, failedTasks, 0, "No task should have failed")
 	assert.Nil(t, trs.FirstError(), "There should be no errors")

libs/pubsub/pubsub_test.go

@@ -273,11 +273,11 @@ func TestResubscribe(t *testing.T) {
 	defer s.Stop()
 
 	ctx := context.Background()
-	subscription, err := s.Subscribe(ctx, clientID, query.Empty{})
+	_, err := s.Subscribe(ctx, clientID, query.Empty{})
 	require.NoError(t, err)
 	err = s.Unsubscribe(ctx, clientID, query.Empty{})
 	require.NoError(t, err)
-	subscription, err = s.Subscribe(ctx, clientID, query.Empty{})
+	subscription, err := s.Subscribe(ctx, clientID, query.Empty{})
 	require.NoError(t, err)
 
 	err = s.Publish(ctx, "Cable")