diff --git a/dist/index.js b/dist/index.js
index 3992650a6..5fa23c3f1 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -1266,6 +1266,46 @@ const windowsRelease = release => {
 module.exports = windowsRelease;
 
 
+/***/ }),
+
+/***/ 81:
+/***/ (function(__unusedmodule, exports, __webpack_require__) {
+
+"use strict";
+
+var __importStar = (this && this.__importStar) || function (mod) {
+    if (mod && mod.__esModule) return mod;
+    var result = {};
+    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k];
+    result["default"] = mod;
+    return result;
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+const assert = __importStar(__webpack_require__(357));
+const url_1 = __webpack_require__(835);
+function getApiUrl() {
+    return process.env['GITHUB_API_URL'] || 'https://api.github.com';
+}
+exports.getApiUrl = getApiUrl;
+function getFetchUrl(settings) {
+    assert.ok(settings.repositoryOwner, 'settings.repositoryOwner must be defined');
+    assert.ok(settings.repositoryName, 'settings.repositoryName must be defined');
+    const serviceUrl = getServerUrl();
+    const encodedOwner = encodeURIComponent(settings.repositoryOwner);
+    const encodedName = encodeURIComponent(settings.repositoryName);
+    if (settings.sshKey) {
+        return `git@${serviceUrl.hostname}:${encodedOwner}/${encodedName}.git`;
+    }
+    // "origin" is SCHEME://HOSTNAME[:PORT]
+    return `${serviceUrl.origin}/${encodedOwner}/${encodedName}`;
+}
+exports.getFetchUrl = getFetchUrl;
+function getServerUrl() {
+    return new url_1.URL(process.env['GITHUB_URL'] || 'https://github.com');
+}
+exports.getServerUrl = getServerUrl;
+
+
 /***/ }),
 
 /***/ 87:
@@ -5109,9 +5149,9 @@ const os = __importStar(__webpack_require__(87));
 const path = __importStar(__webpack_require__(622));
 const regexpHelper = __importStar(__webpack_require__(528));
 const stateHelper = __importStar(__webpack_require__(153));
+const urlHelper = __importStar(__webpack_require__(81));
 const v4_1 = __importDefault(__webpack_require__(826));
 const IS_WINDOWS = process.platform === 'win32';
-const HOSTNAME = 'github.com';
 const SSH_COMMAND_KEY = 'core.sshCommand';
 function createAuthHelper(git, settings) {
     return new GitAuthHelper(git, settings);
@@ -5119,9 +5159,6 @@ function createAuthHelper(git, settings) {
 exports.createAuthHelper = createAuthHelper;
 class GitAuthHelper {
     constructor(gitCommandManager, gitSourceSettings) {
-        this.tokenConfigKey = `http.https://${HOSTNAME}/.extraheader`;
-        this.insteadOfKey = `url.https://${HOSTNAME}/.insteadOf`;
-        this.insteadOfValue = `git@${HOSTNAME}:`;
         this.sshCommand = '';
         this.sshKeyPath = '';
         this.sshKnownHostsPath = '';
@@ -5129,10 +5166,15 @@ class GitAuthHelper {
         this.git = gitCommandManager;
         this.settings = gitSourceSettings || {};
         // Token auth header
+        const serverUrl = urlHelper.getServerUrl();
+        this.tokenConfigKey = `http.${serverUrl.origin}/.extraheader`; // "origin" is SCHEME://HOSTNAME[:PORT]
         const basicCredential = Buffer.from(`x-access-token:${this.settings.authToken}`, 'utf8').toString('base64');
         core.setSecret(basicCredential);
         this.tokenPlaceholderConfigValue = `AUTHORIZATION: basic ***`;
         this.tokenConfigValue = `AUTHORIZATION: basic ${basicCredential}`;
+        // Instead of SSH URL
+        this.insteadOfKey = `url.${serverUrl.origin}/.insteadOf`; // "origin" is SCHEME://HOSTNAME[:PORT]
+        this.insteadOfValue = `git@${serverUrl.hostname}:`;
     }
     configureAuth() {
         return __awaiter(this, void 0, void 0, function* () {
@@ -5797,14 +5839,12 @@ const io = __importStar(__webpack_require__(1));
 const path = __importStar(__webpack_require__(622));
 const refHelper = __importStar(__webpack_require__(227));
 const stateHelper = __importStar(__webpack_require__(153));
-const hostname = 'github.com';
+const urlHelper = __importStar(__webpack_require__(81));
 function getSource(settings) {
     return __awaiter(this, void 0, void 0, function* () {
         // Repository URL
         core.info(`Syncing repository: ${settings.repositoryOwner}/${settings.repositoryName}`);
-        const repositoryUrl = settings.sshKey
-            ? `git@${hostname}:${encodeURIComponent(settings.repositoryOwner)}/${encodeURIComponent(settings.repositoryName)}.git`
-            : `https://${hostname}/${encodeURIComponent(settings.repositoryOwner)}/${encodeURIComponent(settings.repositoryName)}`;
+        const repositoryUrl = urlHelper.getFetchUrl(settings);
         // Remove conflicting file path
         if (fsHelper.fileExistsSync(settings.repositoryPath)) {
             yield io.rmRF(settings.repositoryPath);
@@ -9159,6 +9199,7 @@ const io = __importStar(__webpack_require__(1));
 const path = __importStar(__webpack_require__(622));
 const retryHelper = __importStar(__webpack_require__(587));
 const toolCache = __importStar(__webpack_require__(533));
+const urlHelper = __importStar(__webpack_require__(81));
 const v4_1 = __importDefault(__webpack_require__(826));
 const IS_WINDOWS = process.platform === 'win32';
 function downloadRepository(authToken, owner, repo, ref, commit, repositoryPath) {
@@ -9209,7 +9250,7 @@ function downloadRepository(authToken, owner, repo, ref, commit, repositoryPath)
 exports.downloadRepository = downloadRepository;
 function downloadArchive(authToken, owner, repo, ref, commit) {
     return __awaiter(this, void 0, void 0, function* () {
-        const octokit = new github.GitHub(authToken);
+        const octokit = new github.GitHub(authToken, { baseUrl: urlHelper.getApiUrl() });
         const params = {
             owner: owner,
             repo: repo,
diff --git a/src/git-auth-helper.ts b/src/git-auth-helper.ts
index 06e89125c..92763b893 100644
--- a/src/git-auth-helper.ts
+++ b/src/git-auth-helper.ts
@@ -7,12 +7,12 @@ import * as os from 'os'
 import * as path from 'path'
 import * as regexpHelper from './regexp-helper'
 import * as stateHelper from './state-helper'
+import * as urlHelper from './url-helper'
 import {default as uuid} from 'uuid/v4'
 import {IGitCommandManager} from './git-command-manager'
 import {IGitSourceSettings} from './git-source-settings'
 
 const IS_WINDOWS = process.platform === 'win32'
-const HOSTNAME = 'github.com'
 const SSH_COMMAND_KEY = 'core.sshCommand'
 
 export interface IGitAuthHelper {
@@ -33,15 +33,15 @@ export function createAuthHelper(
 class GitAuthHelper {
   private readonly git: IGitCommandManager
   private readonly settings: IGitSourceSettings
-  private readonly tokenConfigKey: string = `http.https://${HOSTNAME}/.extraheader`
+  private readonly tokenConfigKey: string
+  private readonly tokenConfigValue: string
   private readonly tokenPlaceholderConfigValue: string
-  private readonly insteadOfKey: string = `url.https://${HOSTNAME}/.insteadOf`
-  private readonly insteadOfValue: string = `git@${HOSTNAME}:`
+  private readonly insteadOfKey: string
+  private readonly insteadOfValue: string
   private sshCommand = ''
   private sshKeyPath = ''
   private sshKnownHostsPath = ''
   private temporaryHomePath = ''
-  private tokenConfigValue: string
 
   constructor(
     gitCommandManager: IGitCommandManager,
@@ -51,6 +51,8 @@ class GitAuthHelper {
     this.settings = gitSourceSettings || (({} as unknown) as IGitSourceSettings)
 
     // Token auth header
+    const serverUrl = urlHelper.getServerUrl()
+    this.tokenConfigKey = `http.${serverUrl.origin}/.extraheader` // "origin" is SCHEME://HOSTNAME[:PORT]
     const basicCredential = Buffer.from(
       `x-access-token:${this.settings.authToken}`,
       'utf8'
@@ -58,6 +60,10 @@ class GitAuthHelper {
     core.setSecret(basicCredential)
     this.tokenPlaceholderConfigValue = `AUTHORIZATION: basic ***`
     this.tokenConfigValue = `AUTHORIZATION: basic ${basicCredential}`
+
+    // Instead of SSH URL
+    this.insteadOfKey = `url.${serverUrl.origin}/.insteadOf` // "origin" is SCHEME://HOSTNAME[:PORT]
+    this.insteadOfValue = `git@${serverUrl.hostname}:`
   }
 
   async configureAuth(): Promise<void> {
diff --git a/src/git-source-provider.ts b/src/git-source-provider.ts
index 4bce7021d..85806bb15 100644
--- a/src/git-source-provider.ts
+++ b/src/git-source-provider.ts
@@ -8,23 +8,16 @@ import * as io from '@actions/io'
 import * as path from 'path'
 import * as refHelper from './ref-helper'
 import * as stateHelper from './state-helper'
+import * as urlHelper from './url-helper'
 import {IGitCommandManager} from './git-command-manager'
 import {IGitSourceSettings} from './git-source-settings'
 
-const hostname = 'github.com'
-
 export async function getSource(settings: IGitSourceSettings): Promise<void> {
   // Repository URL
   core.info(
     `Syncing repository: ${settings.repositoryOwner}/${settings.repositoryName}`
   )
-  const repositoryUrl = settings.sshKey
-    ? `git@${hostname}:${encodeURIComponent(
-        settings.repositoryOwner
-      )}/${encodeURIComponent(settings.repositoryName)}.git`
-    : `https://${hostname}/${encodeURIComponent(
-        settings.repositoryOwner
-      )}/${encodeURIComponent(settings.repositoryName)}`
+  const repositoryUrl = urlHelper.getFetchUrl(settings)
 
   // Remove conflicting file path
   if (fsHelper.fileExistsSync(settings.repositoryPath)) {
diff --git a/src/github-api-helper.ts b/src/github-api-helper.ts
index 83a2b869e..df11a855b 100644
--- a/src/github-api-helper.ts
+++ b/src/github-api-helper.ts
@@ -6,6 +6,7 @@ import * as io from '@actions/io'
 import * as path from 'path'
 import * as retryHelper from './retry-helper'
 import * as toolCache from '@actions/tool-cache'
+import * as urlHelper from './url-helper'
 import {default as uuid} from 'uuid/v4'
 import {ReposGetArchiveLinkParams} from '@octokit/rest'
 
@@ -74,7 +75,7 @@ async function downloadArchive(
   ref: string,
   commit: string
 ): Promise<Buffer> {
-  const octokit = new github.GitHub(authToken)
+  const octokit = new github.GitHub(authToken, {baseUrl: urlHelper.getApiUrl()})
   const params: ReposGetArchiveLinkParams = {
     owner: owner,
     repo: repo,
diff --git a/src/url-helper.ts b/src/url-helper.ts
new file mode 100644
index 000000000..3e0e142b6
--- /dev/null
+++ b/src/url-helper.ts
@@ -0,0 +1,28 @@
+import * as assert from 'assert'
+import {IGitSourceSettings} from './git-source-settings'
+import {URL} from 'url'
+
+export function getApiUrl(): string {
+  return process.env['GITHUB_API_URL'] || 'https://api.github.com'
+}
+
+export function getFetchUrl(settings: IGitSourceSettings): string {
+  assert.ok(
+    settings.repositoryOwner,
+    'settings.repositoryOwner must be defined'
+  )
+  assert.ok(settings.repositoryName, 'settings.repositoryName must be defined')
+  const serviceUrl = getServerUrl()
+  const encodedOwner = encodeURIComponent(settings.repositoryOwner)
+  const encodedName = encodeURIComponent(settings.repositoryName)
+  if (settings.sshKey) {
+    return `git@${serviceUrl.hostname}:${encodedOwner}/${encodedName}.git`
+  }
+
+  // "origin" is SCHEME://HOSTNAME[:PORT]
+  return `${serviceUrl.origin}/${encodedOwner}/${encodedName}`
+}
+
+export function getServerUrl(): URL {
+  return new URL(process.env['GITHUB_URL'] || 'https://github.com')
+}