Tech stack: Go: add `Mocking` section

[qdm12]

• [x] Example production code
• [x] Which mocking library
• [x] Mock generation
• [x] Mock usage
• [x] Mocks with subtests
• [x] Mock continuous integration
• [x] Advanced GoMock
  • [x] Mock calls order
  • [x] Custom GoMock matchers
  • [x] Unpredictable mock arguments

[render[bot]]

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