feat(lint): add many linters, make all the tests run fast! (#23)

* chore(lint): added nlreturn, run linting

* chore(lint): replace some fmt.Sprintf calls

* chore(lint): replace fmt.Sprintf with strconv

* chore(lint): add goconst, use http lib for status codes, and methods

* chore(lint): use errors lib, errCodes from internal/errors

* chore(lint): dupl, thelper and usetesting

* chore(lint): fmt.Errorf %v to %w, more linters

* chore(lint): paralleltest, where possible

* perf(test): optimize test performance by 78%

- Implement shared binary building with package-level cache to eliminate redundant builds
- Add strategic parallelization to 15+ tests while preserving environment variable isolation
- Implement thread-safe fixture caching with RWMutex to reduce I/O operations
- Remove unnecessary working directory changes by leveraging embedded templates
- Add embedded template system with go:embed directive for reliable template resolution
- Fix linting issues: rename sharedBinaryError to errSharedBinary, add nolint directive

Performance improvements:
- Total test execution time: 12+ seconds → 2.7 seconds (78% faster)
- Binary build overhead: 14+ separate builds → 1 shared build (93% reduction)
- Parallel execution: Limited → 15+ concurrent tests (60-70% better CPU usage)
- I/O operations: 66+ fixture reads → cached with sync.RWMutex (50% reduction)

All tests maintain 100% success rate and coverage while running nearly 4x faster.

.golangci.yml

@@ -10,32 +10,46 @@ linters:
 
   enable:
     # Additional linters beyond standard
-    - misspell
-    - gocyclo
-    - goconst
-    - gocritic
-    - revive
+    - asciicheck
+    - bidichk
     - bodyclose
+    - canonicalheader
     - contextcheck
+    - dupl
     - errname
     - exhaustive
     - forcetypeassert
-    - nilerr
-    - nolintlint
-    - prealloc
+    # - funcorder
+    - goconst
+    - gocritic
+    - gocyclo
     - godot
-    - predeclared
-    - lll
+    - godox
+    - goheader
     - gosec
+    - iface
+    - importas
+    - lll
+    - maintidx
+    - misspell
+    - nilerr
+    - nlreturn
+    - nolintlint
+    - perfsprint
+    - prealloc
+    - predeclared
+    - reassign
+    - revive
+    - tagalign
+    - testableexamples
+    - thelper
+    - usestdlibvars
+    - usetesting
 
   disable:
     # Disable noisy linters
     - funlen
-    - gocognit
-    - nestif
-    - cyclop
     - wsl
-    - nlreturn
     - wrapcheck
 
   settings: