fix(datasource/go): Fixes splitting of gitlab go package name

lib/modules/datasource/go/base.spec.ts

@@ -2,6 +2,7 @@ import { mockDeep } from 'jest-mock-extended';
 import { Fixtures } from '../../../../test/fixtures';
 import * as httpMock from '../../../../test/http-mock';
 import { mocked } from '../../../../test/util';
+import { GlobalConfig } from '../../../config/global';
 import * as _hostRules from '../../../util/host-rules';
 import { GitTagsDatasource } from '../git-tags';
 import { GithubTagsDatasource } from '../github-tags';
@@ -394,6 +395,50 @@ describe('modules/datasource/go/base', () => {
 
         expect(res).toBeNull();
       });
+
+      it('it correctly splits a URL where the endpoint is contained', async () => {
+        hostRules.hostType.mockReturnValue('gitlab');
+
+        GlobalConfig.set({ endpoint: 'https://example.com/gitlab/api/v4/' });
+
+        const meta =
+          '<meta name="go-import" content="example.com/gitlab/my-project/my-repo.git git https://example.com/gitlab/my-project/my-repo" />';
+        httpMock
+          .scope('https://example.com')
+          .get('/gitlab/my-project/my-repo.git?go-get=1')
+          .reply(200, meta);
+
+        const res = await BaseGoDatasource.getDatasource(
+          'example.com/gitlab/my-project/my-repo.git',
+        );
+
+
+        expect(res).toEqual({
+          datasource: GitlabTagsDatasource.id,
+          packageName: 'my-project/my-repo',
+          registryUrl: 'https://example.com/gitlab/',
+        });
+
+        GlobalConfig.set({ endpoint: 'https://example.com/gitlab/' });
+
+        httpMock
+          .scope('https://example.com')
+          .get('/gitlab/my-project/my-repo.git?go-get=1')
+          .reply(200, meta);
+
+        const res2 = await BaseGoDatasource.getDatasource(
+          'example.com/gitlab/my-project/my-repo.git',
+        );
+
+        expect(res2).toEqual({
+          datasource: GitlabTagsDatasource.id,
+          packageName: 'my-project/my-repo',
+          registryUrl: 'https://example.com/gitlab/',
+        });
+
+        GlobalConfig.reset();
+        hostRules.hostType.mockReturnValue('');
+      });
     });
   });
 });

lib/modules/datasource/go/base.ts

@@ -1,5 +1,6 @@
 // TODO: types (#22198)
 import URL from 'node:url';
+import { GlobalConfig } from '../../../config/global';
 import { logger } from '../../../logger';
 import { detectPlatform } from '../../../util/common';
 import * as hostRules from '../../../util/host-rules';
@@ -154,17 +155,35 @@ export class BaseGoDatasource {
       const parsedUrl = URL.parse(goSourceUrl);
 
       // TODO: `parsedUrl.pathname` can be undefined
-      const packageName = trimLeadingSlash(`${parsedUrl.pathname}`);
+      let packageName = trimLeadingSlash(`${parsedUrl.pathname}`);
 
-      const registryUrl = `${parsedUrl.protocol}//${parsedUrl.host}`;
+      const endpoint = GlobalConfig.get('endpoint');
+
+      const endpointPrefix = endpoint?.match('https://[^/]*/(.*?/)(api/v4/?)?');
+
+      if (endpointPrefix) {
+        packageName = packageName.replace(endpointPrefix[1], '');
+      }
+
+      const registryUrl =
+        endpoint?.replaceAll('api/v4/', '') ??
+        `${parsedUrl.protocol}//${parsedUrl.host}`;
 
       // a .git path indicates a concrete git repository, which can be different from metadata returned by gitlab
       const vcsIndicatedModule = BaseGoDatasource.gitVcsRegexp.exec(goModule);
       if (vcsIndicatedModule?.groups?.module) {
+        if (endpointPrefix) {
+          packageName = vcsIndicatedModule.groups?.module.replace(
+            endpointPrefix[1],
+            '',
+          );
+        } else {
+          packageName = vcsIndicatedModule.groups?.module;
+        }
         return {
           datasource: GitlabTagsDatasource.id,
           registryUrl,
-          packageName: vcsIndicatedModule.groups?.module,
+          packageName,
         };
       }