fix: prefer globalThis instead of window to support webworkers

There is no `window` in either WebWorkers and ServiceWorkers.

packages/opentelemetry-core/src/platform/browser/environment.ts

@@ -21,11 +21,12 @@ import {
   parseEnvironment,
 } from '../../utils/environment';
 
+const _global = typeof globalThis === 'object' ? globalThis : window;
+
 /**
  * Gets the environment variables
  */
 export function getEnv(): Required<ENVIRONMENT> {
-  const _window = window as typeof window & RAW_ENVIRONMENT;
-  const globalEnv = parseEnvironment(_window);
+  const globalEnv = parseEnvironment(_global as typeof globalThis & RAW_ENVIRONMENT);
   return Object.assign({}, DEFAULT_ENVIRONMENT, globalEnv);
 }

packages/opentelemetry-core/test/platform/browser/environment.test.ts

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import * as assert from 'assert';
+import { getEnv } from '../../../src/platform/browser/environment';
+
+describe('getEnv', () => {
+  it('get environs in window', () => {
+    const env = getEnv();
+    assert.strictEqual(typeof env, 'object');
+  });
+});