Use latest golangci-lint release and update linter list. (#484)

* ci: Update linter to 1.59.1.

Also remove deprecated linter "vetshadow", its functionality is now
included in the "govet" linter.

* ci: Add new linters.

- fatcontext - Detects nested contexts in loops.
- mirror - Reports wrong mirror patterns of bytes/strings usage.
- nilnil - Checks that there is no simultaneous return of nil error and
  an invalid value.
- usestdlibvars - detect the possibility to use variables/constants from
  the Go standard library.

.github/workflows/go.yml

@@ -17,6 +17,6 @@ jobs:
       - name: Build
         run: go build ./...
       - name: Install Linters
-        run: "curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.58.1"
+        run: "curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b $(go env GOPATH)/bin v1.59.1"
       - name: Test and Lint
         run: ./run_tests.sh

.golangci.yml

@@ -14,6 +14,7 @@ linters:
     - errorlint
     - exhaustive
     - exportloopref
+    - fatcontext
     - goconst
     - godot
     - gofmt
@@ -22,8 +23,10 @@ linters:
     - govet
     - ineffassign
     - makezero
+    - mirror
     - misspell
     - nilerr
+    - nilnil
     - nosprintfhostport
     - prealloc
     - predeclared
@@ -33,6 +36,6 @@ linters:
     - tparallel
     - typecheck
     - unconvert
+    - usestdlibvars
     - unparam
     - unused
-    - vetshadow