Add the config file for golangci-lint

This uses most of the settings from the default golangci-lint config,
but a few are changed after using it on my own projects. This will
require some codebase changes to get the linter to pass, but just adding
the config file for now.

.golangci.yaml

@@ -0,0 +1,103 @@
+linters-settings:
+  dupl:
+    threshold: 100
+  funlen:
+    lines: 100
+    statements: 50
+  gci:
+    local-prefixes: github.com/udemy/schema-vault
+  goconst:
+    min-len: 2
+    min-occurrences: 2
+  gocritic:
+    enabled-tags:
+      - diagnostic
+      - experimental
+      - opinionated
+      - performance
+      - style
+    disabled-checks:
+      - dupImport
+      - ifElseChain
+      - octalLiteral
+      - whyNoLint
+      - wrapperFunc
+    settings:
+      rangeValCopy:
+        sizeThreshold: 512
+  gocyclo:
+    min-complexity: 15
+  goimports:
+    local-prefixes: github.com/udemy/schema-vault
+  golint:
+    min-confidence: 0
+  gomnd:
+    settings:
+      mnd:
+        checks: argument,case,condition,return
+  govet:
+    check-shadowing: true
+  maligned:
+    suggest-new: true
+  misspell:
+    locale: US
+  nolintlint:
+    allow-leading-space: true
+    allow-unused: false
+    require-explanation: false
+    require-specific: false
+linters:
+  disable-all: true
+  enable:
+    - bodyclose
+    - deadcode
+    - depguard
+    - dogsled
+    - dupl
+    - errcheck
+    - exhaustive
+    - funlen
+    - gochecknoinits
+    - goconst
+    - gocritic
+    - gocyclo
+    - goimports
+    - gofmt
+    - golint
+    - gomnd
+    - goprintffuncname
+    - gosec
+    - gosimple
+    - govet
+    - ineffassign
+    - interfacer
+    - misspell
+    - nakedret
+    - noctx
+    - nolintlint
+    - rowserrcheck
+    - scopelint
+    - staticcheck
+    - structcheck
+    - stylecheck
+    - typecheck
+    - unconvert
+    - unparam
+    - unused
+    - varcheck
+    - whitespace
+issues:
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - gomnd
+    - linters:
+        - gocritic
+      text: "unnecessaryDefer:"
+run:
+  timeout: 1m
+  issues-exit-code: 1
+  tests: true
+  skip-dirs-use-default: true
+  allow-parallel-runners: true
+