diff --git a/.concourse/tasks/test.yml b/.concourse/tasks/test.yml
index 50467c9..fda54dc 100644
--- a/.concourse/tasks/test.yml
+++ b/.concourse/tasks/test.yml
@@ -21,4 +21,4 @@ run:
   args:
     - -ce
     - |
-      go run gotest.tools/gotestsum@latest ./...
+      go run gotest.tools/gotestsum@latest -f pkgname-and-test-fails -- -race -shuffle=on ./...
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..8b80ccd
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,142 @@
+linters-settings:
+  dupl:
+    threshold: 100
+  funlen:
+    lines: 100
+    statements: 50
+  gci:
+    local-prefixes: code.icb4dc0.de/prskr/gapr
+  gosec:
+    excludes:
+      - G404
+  goconst:
+    min-len: 2
+    min-occurrences: 2
+  gocritic:
+    enabled-tags:
+      - diagnostic
+      - opinionated
+      - performance
+    disabled-checks:
+      - ifElseChain
+      - octalLiteral
+      - wrapperFunc
+      # see https://github.com/golangci/golangci-lint/issues/2649
+      - hugeParam
+      - rangeValCopy
+    # settings:
+    #   hugeParam:
+    #     sizeThreshold: 200
+  gocyclo:
+    min-complexity: 15
+  goimports:
+    local-prefixes: code.icb4dc0.de/prskr/gapr
+  golint:
+    min-confidence: 0
+  gomnd:
+    settings:
+      mnd:
+        # don't include the "operation" and "assign"
+        checks:
+          - argument
+          - case
+          - condition
+          - return
+  gomoddirectives:
+    replace-allow-list: [ ]
+
+  govet:
+    check-shadowing: true
+    enable-all: true
+    disable:
+      - fieldalignment
+      # see https://github.com/golangci/golangci-lint/issues/2649
+      - nilness
+      - unusedwrite
+  importas:
+    no-unaliased: true
+    alias: [ ]
+  lll:
+    line-length: 140
+  misspell:
+    locale: US
+  nolintlint:
+    allow-leading-space: true # don't require machine-readable nolint directives (i.e. with no leading space)
+    allow-unused: false # report any unused nolint directives
+    require-explanation: false # don't require an explanation for nolint directives
+    require-specific: false # don't require nolint directives to be specific about which linter is being skipped
+
+linters:
+  disable-all: true
+  enable:
+    - contextcheck
+    - dogsled
+    - dupl
+    - errcheck
+    - errchkjson
+    - errname
+    - errorlint
+    - exhaustive
+    - exportloopref
+    - funlen
+    - gocognit
+    - goconst
+    # - gocritic
+    - gocyclo
+    - godox
+    - gofumpt
+    - goimports
+    - gomoddirectives
+    - gomnd
+    - gosec
+    - gosimple
+    - govet
+    - importas
+    - ineffassign
+    - ireturn
+    - lll
+    - misspell
+    - nakedret
+    - nestif
+    - nilnil
+    - noctx
+    - nolintlint
+    - paralleltest
+    - prealloc
+    - predeclared
+    - promlinter
+    - staticcheck
+    - stylecheck
+    - testpackage
+    - thelper
+    # - typecheck
+    - unconvert
+    - unparam
+    - whitespace
+    - unused
+    - wastedassign
+
+issues:
+  # Excluding configuration per-path, per-linter, per-text and per-source
+  exclude-rules:
+    - path: _test\.go
+      linters:
+        - dupl
+        - funlen
+        - gocognit
+        - gomnd
+        - govet
+        - dupl
+    - path: magefiles/.*\.go
+      linters:
+        - typecheck
+
+run:
+  build-tags: [ ]
+  skip-dirs: [ ]
+  skip-files:
+    - ".*\\.pb\\.go$"
+    - ".*.mock.\\.go$"
+  modules-download-mode: readonly
+  go: "1.18"
+  timeout: 10m
diff --git a/gapr.go b/gapr.go
index 44ea539..8276640 100644
--- a/gapr.go
+++ b/gapr.go
@@ -44,6 +44,7 @@ func (g *Gapr) Map(input any) (any, error) {
 		return nil, ErrNotSupportedType
 	}
 
+	//nolint:exhaustive // handled with default case
 	switch t.Kind() {
 	case reflect.Map:
 		return g.mapMap(t, v)
@@ -114,7 +115,7 @@ func (g *Gapr) mapMap(t reflect.Type, v reflect.Value) (any, error) {
 func (g *Gapr) mapSliceOrArray(v reflect.Value) (any, error) {
 	var (
 		length = v.Len()
-		target = reflect.ValueOf(make([]any, length, length))
+		target = reflect.ValueOf(make([]any, length))
 	)
 
 	for i := 0; i < length; i++ {
@@ -170,6 +171,7 @@ func canMap(t reflect.Type, v reflect.Value) bool {
 		t = reflect.TypeOf(v.Interface())
 	}
 
+	//nolint:exhaustive // handled with default case
 	switch t.Kind() {
 	case reflect.Struct, reflect.Map, reflect.Slice, reflect.Array:
 		return true
diff --git a/gapr_test.go b/gapr_test.go
index 6408ee5..b09a09d 100644
--- a/gapr_test.go
+++ b/gapr_test.go
@@ -8,6 +8,8 @@ import (
 )
 
 func TestGapr_Map(t *testing.T) {
+	t.Parallel()
+
 	type args struct {
 		input any
 		opts  []gapr.Option
@@ -148,12 +150,20 @@ func TestGapr_Map(t *testing.T) {
 					},
 				},
 			},
-			want:    nil,
+			want: map[string]any{
+				"Hello": map[string]any{
+					"givenName": "Ted",
+					"Surname":   "Tester",
+				},
+			},
 			wantErr: false,
 		},
 	}
 	for _, tt := range tests {
+		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
 			g := gapr.New(tt.args.opts...)
 			got, err := g.Map(tt.args.input)
 			if (got == nil) == (err == nil) {
diff --git a/keys.go b/keys.go
index 29375a1..e29ad86 100644
--- a/keys.go
+++ b/keys.go
@@ -16,6 +16,9 @@ func (f KeyMapperFunc) MapKey(orig string) string {
 }
 
 var (
+	identityKeyMapper KeyMapper = KeyMapperFunc(func(orig string) string {
+		return orig
+	})
 	LowercaseKeyMapper KeyMapper = KeyMapperFunc(func(orig string) string {
 		return strings.ToLower(orig)
 	})
@@ -29,8 +32,8 @@ var (
 	PascalCaseKeyMapper = genericFirstKeyMapper(unicode.ToUpper)
 )
 
-func genericFirstKeyMapper(m func(r rune) rune) KeyMapper {
-	return KeyMapperFunc(func(orig string) string {
+func genericFirstKeyMapper(m func(r rune) rune) KeyMapperFunc {
+	return func(orig string) string {
 		if len(orig) < 1 {
 			return ""
 		}
@@ -43,5 +46,5 @@ func genericFirstKeyMapper(m func(r rune) rune) KeyMapper {
 		}
 
 		return string(mapped)
-	})
+	}
 }
diff --git a/options.go b/options.go
index f67d9e2..563d1be 100644
--- a/options.go
+++ b/options.go
@@ -2,22 +2,29 @@ package gapr
 
 import "time"
 
-func WithRandomSeed(i int64) Option {
-	return optionFunc(func(o *options) {
+func WithRandomSeed(i int64) optionFunc {
+	return func(o *options) {
 		o.RandomSeed = i
-	})
+	}
 }
 
-func WithTagName(tag string) Option {
-	return optionFunc(func(o *options) {
+func WithTagName(tag string) optionFunc {
+	return func(o *options) {
 		o.TagName = tag
-	})
+	}
+}
+
+func WithMapper(mapper KeyMapper) optionFunc {
+	return func(o *options) {
+		o.Mapper = mapper
+	}
 }
 
 func defaultOptions() options {
 	return options{
 		TagName:    "gapr",
 		RandomSeed: time.Now().UTC().Unix(),
+		Mapper:     identityKeyMapper,
 	}
 }
 
@@ -34,4 +41,5 @@ func (f optionFunc) apply(o *options) {
 type options struct {
 	TagName    string
 	RandomSeed int64
+	Mapper     KeyMapper
 }