*: fix some lint issues

Mostly gathered these using golangci-lint's deadcode and ineffassign
linters.

Signed-off-by: Stephan Renatus <srenatus@chef.io>

server/oauth2.go

@@ -89,6 +89,7 @@ func tokenErr(w http.ResponseWriter, typ, description string, statusCode int) er
 	return nil
 }
 
+// nolint
 const (
 	errInvalidRequest          = "invalid_request"
 	errUnauthorizedClient      = "unauthorized_client"

server/rotation.go

@@ -92,7 +92,6 @@ func (s *Server) startKeyRotation(ctx context.Context, strategy rotationStrategy
 			}
 		}
 	}()
-	return
 }
 
 func (k keyRotater) rotate() error {

server/server.go

@@ -426,7 +426,6 @@ func (s *Server) startGarbageCollection(ctx context.Context, frequency time.Dura
 			}
 		}
 	}()
-	return
 }
 
 // ConnectorConfig is a configuration that can open a connector.

server/server_test.go

@@ -552,7 +552,6 @@ func TestOAuth2CodeFlow(t *testing.T) {
 					t.Errorf("state did not match, want=%q got=%q", state, gotState)
 				}
 				w.WriteHeader(http.StatusOK)
-				return
 			}))
 
 			defer oauth2Client.Close()
@@ -1204,7 +1203,6 @@ func TestRefreshTokenFlow(t *testing.T) {
 			t.Errorf("state did not match, want=%q got=%q", state, gotState)
 		}
 		w.WriteHeader(http.StatusOK)
-		return
 	}))
 	defer oauth2Client.server.Close()
 
@@ -1242,8 +1240,7 @@ func TestRefreshTokenFlow(t *testing.T) {
 	}
 
 	// try to refresh expired token with old refresh token.
-	newToken, err := oauth2Client.config.TokenSource(ctx, tok).Token()
-	if newToken != nil {
-		t.Errorf("Token refreshed with invalid refresh token.")
+	if _, err := oauth2Client.config.TokenSource(ctx, tok).Token(); err == nil {
+		t.Errorf("Token refreshed with invalid refresh token, error expected.")
 	}
 }