feat(manager/go): support modules without paths (#31155)

lib/modules/manager/gomod/line-parser.spec.ts

@@ -107,6 +107,28 @@ describe('modules/manager/gomod/line-parser', () => {
     });
   });
 
+  it('should parse go modules without paths - 1', () => {
+    const line = 'require tailscale.com v1.72.0';
+    const res = parseLine(line);
+    expect(res).toStrictEqual({
+      currentValue: 'v1.72.0',
+      datasource: 'go',
+      depName: 'tailscale.com',
+      depType: 'require',
+    });
+  });
+
+  it('should parse go modules without paths - 2', () => {
+    const line = 'require foo.tailscale.com v1.72.0';
+    const res = parseLine(line);
+    expect(res).toStrictEqual({
+      currentValue: 'v1.72.0',
+      datasource: 'go',
+      depName: 'foo.tailscale.com',
+      depType: 'require',
+    });
+  });
+
   it('should parse require multi-line definition with quotes', () => {
     const line = '        "foo/foo" v1.2';
     const res = parseLine(line);

lib/modules/manager/gomod/line-parser.ts

@@ -10,7 +10,7 @@ function trimQuotes(str: string): string {
 }
 
 const requireRegex = regEx(
-  /^(?<keyword>require)?\s+(?<module>[^\s]+\/[^\s]+)\s+(?<version>[^\s]+)(?:\s*\/\/\s*(?<comment>[^\s]+)\s*)?$/,
+  /^(?<keyword>require)?\s+(?<module>[^\s]+\/?[^\s]+)\s+(?<version>[^\s]+)(?:\s*\/\/\s*(?<comment>[^\s]+)\s*)?$/,
 );
 
 const replaceRegex = regEx(