diff --git a/.github/workflows/bench.yml b/.github/workflows/bench.yml
index 0e6bddc..d750b9d 100644
--- a/.github/workflows/bench.yml
+++ b/.github/workflows/bench.yml
@@ -21,7 +21,7 @@ env:
   GO111MODULE: "on"
   CACHE_BENCHMARK: "off"    # Enables benchmark result reuse between runs, may skew latency results.
   RUN_BASE_BENCHMARK: "on"  # Runs benchmark for PR base in case benchmark result is missing.
-  GO_VERSION: 1.18.x
+  GO_VERSION: 1.19.x
 jobs:
   bench:
     runs-on: ubuntu-latest
diff --git a/.github/workflows/cloc.yml b/.github/workflows/cloc.yml
index d6ff20d..619ca74 100644
--- a/.github/workflows/cloc.yml
+++ b/.github/workflows/cloc.yml
@@ -24,7 +24,9 @@ jobs:
       - name: Count Lines Of Code
         id: loc
         run: |
-          curl -sLO https://github.com/vearutop/sccdiff/releases/download/v1.0.1/linux_amd64.tar.gz && tar xf linux_amd64.tar.gz
+          curl -sLO https://github.com/vearutop/sccdiff/releases/download/v1.0.3/linux_amd64.tar.gz && tar xf linux_amd64.tar.gz
+          sccdiff_hash=$(git hash-object ./sccdiff)
+          [ "$sccdiff_hash" == "ae8a07b687bd3dba60861584efe724351aa7ff63" ] || (echo "::error::unexpected hash for sccdiff, possible tampering: $sccdiff_hash" && exit 1)
           OUTPUT=$(cd pr && ../sccdiff -basedir ../base)
           echo "${OUTPUT}"
           OUTPUT="${OUTPUT//$'\n'/%0A}"
diff --git a/.github/workflows/golangci-lint.yml b/.github/workflows/golangci-lint.yml
index b4f7600..bf0bcdb 100644
--- a/.github/workflows/golangci-lint.yml
+++ b/.github/workflows/golangci-lint.yml
@@ -21,13 +21,13 @@ jobs:
     steps:
       - uses: actions/setup-go@v3
         with:
-          go-version: 1.18.x
+          go-version: 1.19.x
       - uses: actions/checkout@v2
       - name: golangci-lint
-        uses: golangci/golangci-lint-action@v3.1.0
+        uses: golangci/golangci-lint-action@v3.2.0
         with:
           # Required: the version of golangci-lint is required and must be specified without patch version: we always use the latest patch version.
-          version: v1.45.2
+          version: v1.50.0
 
           # Optional: working directory, useful for monorepos
           # working-directory: somedir
diff --git a/.github/workflows/gorelease.yml b/.github/workflows/gorelease.yml
index 429d5ed..6267500 100644
--- a/.github/workflows/gorelease.yml
+++ b/.github/workflows/gorelease.yml
@@ -9,7 +9,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  GO_VERSION: 1.18.x
+  GO_VERSION: 1.19.x
 jobs:
   gorelease:
     runs-on: ubuntu-latest
@@ -35,12 +35,12 @@ jobs:
         with:
           path: |
             ~/go/bin/gorelease
-          key: ${{ runner.os }}-gorelease
+          key: ${{ runner.os }}-gorelease-generic
       - name: Gorelease
         id: gorelease
         run: |
           test -e ~/go/bin/gorelease || go install golang.org/x/exp/cmd/gorelease@latest
-          OUTPUT=$(gorelease || exit 0)
+          OUTPUT=$(gorelease 2>&1 || exit 0)
           echo "${OUTPUT}"
           OUTPUT="${OUTPUT//$'\n'/%0A}"
           echo "::set-output name=report::$OUTPUT"
diff --git a/.github/workflows/test-unit.yml b/.github/workflows/test-unit.yml
index a1d30c9..94441bd 100644
--- a/.github/workflows/test-unit.yml
+++ b/.github/workflows/test-unit.yml
@@ -16,11 +16,12 @@ env:
   GO111MODULE: "on"
   RUN_BASE_COVERAGE: "on"  # Runs test for PR base in case base test coverage is missing.
   COV_GO_VERSION: 1.18.x   # Version of Go to collect coverage
+  TARGET_DELTA_COV: 90     # Target coverage of changed lines, in percents
 jobs:
   test:
     strategy:
       matrix:
-        go-version: [ 1.16.x, 1.17.x, 1.18.x, tip ]
+        go-version: [ 1.16.x, 1.17.x, 1.18.x, 1.19.x ]
     runs-on: ubuntu-latest
     steps:
       - name: Install Go stable
@@ -28,6 +29,7 @@ jobs:
         uses: actions/setup-go@v3
         with:
           go-version: ${{ matrix.go-version }}
+
       - name: Install Go tip
         if: matrix.go-version == 'tip'
         run: |
@@ -37,8 +39,10 @@ jobs:
           tar -C ~/sdk/gotip -xzf gotip.tar.gz
           ~/sdk/gotip/bin/go version
           echo "PATH=$HOME/go/bin:$HOME/sdk/gotip/bin/:$PATH" >> $GITHUB_ENV
+
       - name: Checkout code
         uses: actions/checkout@v2
+
       - name: Go cache
         uses: actions/cache@v2
         with:
@@ -51,44 +55,57 @@ jobs:
           key: ${{ runner.os }}-go-cache-${{ hashFiles('**/go.sum') }}
           restore-keys: |
             ${{ runner.os }}-go-cache
+
       - name: Restore base test coverage
         id: base-coverage
-        if: matrix.go-version == env.COV_GO_VERSION
+        if: matrix.go-version == env.COV_GO_VERSION && github.event.pull_request.base.sha != ''
         uses: actions/cache@v2
         with:
           path: |
             unit-base.txt
           # Use base sha for PR or new commit hash for master/main push in test result key.
           key: ${{ runner.os }}-unit-test-coverage-${{ (github.event.pull_request.base.sha != github.event.after) && github.event.pull_request.base.sha || github.event.after }}
-      - name: Checkout base code
-        if: matrix.go-version == env.COV_GO_VERSION && env.RUN_BASE_COVERAGE == 'on' && steps.base-coverage.outputs.cache-hit != 'true' && github.event.pull_request.base.sha != ''
-        uses: actions/checkout@v2
-        with:
-          ref: ${{ github.event.pull_request.base.sha }}
-          path: __base
+
       - name: Run test for base code
         if: matrix.go-version == env.COV_GO_VERSION && env.RUN_BASE_COVERAGE == 'on' && steps.base-coverage.outputs.cache-hit != 'true' && github.event.pull_request.base.sha != ''
         run: |
-          cd __base
-          make | grep test-unit && (make test-unit && go tool cover -func=./unit.coverprofile | sed -e 's/.go:[0-9]*:\t/.go\t/g' | sed -e 's/\t\t*/\t/g'  > ../unit-base.txt) || echo "No test-unit in base"
+          git fetch origin master ${{ github.event.pull_request.base.sha }}
+          HEAD=$(git rev-parse HEAD)
+          git reset --hard ${{ github.event.pull_request.base.sha }}
+          (make test-unit && go tool cover -func=./unit.coverprofile > unit-base.txt) || echo "No test-unit in base"
+          git reset --hard $HEAD
+
       - name: Test
         id: test
         run: |
           make test-unit
-          go tool cover -func=./unit.coverprofile | sed -e 's/.go:[0-9]*:\t/.go\t/g' | sed -e 's/\t\t*/\t/g'  > unit.txt
-          OUTPUT=$(test -e unit-base.txt && (diff unit-base.txt unit.txt || exit 0) || cat unit.txt)
-          echo "${OUTPUT}"
-          OUTPUT="${OUTPUT//$'\n'/%0A}"
+          go tool cover -func=./unit.coverprofile > unit.txt
           TOTAL=$(grep 'total:' unit.txt)
           echo "${TOTAL}"
-          echo "::set-output name=diff::$OUTPUT"
           echo "::set-output name=total::$TOTAL"
-      - name: Store base coverage
-        if: ${{ github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main' }}
-        run: cp unit.txt unit-base.txt
+
+      - name: Annotate missing test coverage
+        id: annotate
+        if: matrix.go-version == env.COV_GO_VERSION && github.event.pull_request.base.sha != ''
+        run: |
+          curl -sLO https://github.com/vearutop/gocovdiff/releases/download/v1.3.6/linux_amd64.tar.gz && tar xf linux_amd64.tar.gz
+          gocovdiff_hash=$(git hash-object ./gocovdiff)
+          [ "$gocovdiff_hash" == "8e507e0d671d4d6dfb3612309b72b163492f28eb" ] || (echo "::error::unexpected hash for gocovdiff, possible tampering: $gocovdiff_hash" && exit 1)
+          git fetch origin master ${{ github.event.pull_request.base.sha }}
+          REP=$(./gocovdiff -cov unit.coverprofile -gha-annotations gha-unit.txt -delta-cov-file delta-cov-unit.txt -target-delta-cov ${TARGET_DELTA_COV})
+          echo "${REP}"
+          REP="${REP//$'\n'/%0A}"
+          cat gha-unit.txt
+          DIFF=$(test -e unit-base.txt && ./gocovdiff -func-cov unit.txt -func-base-cov unit-base.txt || echo "Missing base coverage file")
+          DIFF="${DIFF//$'\n'/%0A}"
+          TOTAL=$(cat delta-cov-unit.txt)
+          echo "::set-output name=rep::$REP"
+          echo "::set-output name=diff::$DIFF"
+          echo "::set-output name=total::$TOTAL"
+
       - name: Comment Test Coverage
         continue-on-error: true
-        if: matrix.go-version == env.COV_GO_VERSION
+        if: matrix.go-version == env.COV_GO_VERSION && github.event.pull_request.base.sha != ''
         uses: marocchino/sticky-pull-request-comment@v2
         with:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -96,13 +113,23 @@ jobs:
           message: |
             ### Unit Test Coverage
             ${{ steps.test.outputs.total }}
+            ${{ steps.annotate.outputs.total }}
+            <details><summary>Coverage of changed lines</summary>
+            
+            ${{ steps.annotate.outputs.rep }}
+
+            </details>
+
             <details><summary>Coverage diff with base branch</summary>
 
-            ```diff
-            ${{ steps.test.outputs.diff }}
-            ```
+            ${{ steps.annotate.outputs.diff }}
+            
             </details>
 
+      - name: Store base coverage
+        if: ${{ github.ref == 'refs/heads/master' || github.ref == 'refs/heads/main' }}
+        run: cp unit.txt unit-base.txt
+
       - name: Upload code coverage
         if: matrix.go-version == env.COV_GO_VERSION
         uses: codecov/codecov-action@v1
diff --git a/.golangci.yml b/.golangci.yml
index 97710e1..219b387 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -37,6 +37,14 @@ linters:
     - tagliatelle
     - errname
     - ireturn
+    - exhaustruct
+    - nonamedreturns
+    - nosnakecase
+    - structcheck
+    - varcheck
+    - deadcode
+    - testableexamples
+    - dupword
 
 issues:
   exclude-use-default: false
@@ -48,5 +56,13 @@ issues:
         - noctx
         - funlen
         - dupl
+        - structcheck
+        - unused
+        - unparam
+        - nosnakecase
       path: "_test.go"
+    - linters:
+        - errcheck # Error checking omitted for brevity.
+        - gosec
+      path: "example_"
 
diff --git a/Makefile b/Makefile
index 77a5ec3..80dc683 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-#GOLANGCI_LINT_VERSION := "v1.45.2" # Optional configuration to pinpoint golangci-lint version.
+#GOLANGCI_LINT_VERSION := "v1.50.0" # Optional configuration to pinpoint golangci-lint version.
 
 # The head of Makefile determines location of dev-go to include standard targets.
 GO ?= go
diff --git a/error.go b/error.go
index 86111fe..5a9b3e3 100644
--- a/error.go
+++ b/error.go
@@ -87,7 +87,7 @@ func WrapError(ctx context.Context, err error, message string, keysAndValues ...
 //
 // LogError fields from context are also added to error structured data.
 func NewError(ctx context.Context, message string, keysAndValues ...interface{}) error {
-	// nolint:goerr113 // Static errors can be used with WrapError.
+	//nolint:goerr113 // Static errors can be used with WrapError.
 	err := errors.New(message)
 
 	se, ok := newError(ctx, err, keysAndValues...)
@@ -236,6 +236,8 @@ func (se structuredError) MarshalJSON() ([]byte, error) {
 }
 
 // SentinelError is a constant error.
+//
+// See https://dave.cheney.net/2016/04/07/constant-errors for more details.
 type SentinelError string
 
 // Error returns error message.
@@ -300,3 +302,64 @@ func (le labeledError) As(v interface{}) bool {
 func (le labeledError) Unwrap() error {
 	return le.err
 }
+
+// MultiError creates an error with multiple unwrappables.
+//
+// Secondary errors could be checked with errors.Is, errors.As.
+// Error message remains the same with primary error.
+//
+// Multi errors can be used to augment error with multiple
+// checkable perks, without a limitation of single wrapping inheritance.
+func MultiError(primary error, secondary ...error) error {
+	return multi{
+		primary:   primary,
+		secondary: secondary,
+	}
+}
+
+type multi struct {
+	primary   error
+	secondary []error
+}
+
+// Error returns message.
+func (le multi) Error() string {
+	return le.primary.Error()
+}
+
+// Is returns true if err matches primary error or any of secondary.
+func (le multi) Is(err error) bool {
+	if errors.Is(le.primary, err) {
+		return true
+	}
+
+	for _, l := range le.secondary {
+		if errors.Is(err, l) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// As returns true if primary error or any of secondary can be assigned to v.
+//
+// If multiple assignations are possible, only first one is performed.
+func (le multi) As(v interface{}) bool {
+	if errors.As(le.primary, v) {
+		return true
+	}
+
+	for _, l := range le.secondary {
+		if errors.As(l, v) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// Unwrap returns primary error.
+func (le multi) Unwrap() error {
+	return le.primary
+}
diff --git a/error_test.go b/error_test.go
index 5c7bb11..86eed42 100644
--- a/error_test.go
+++ b/error_test.go
@@ -259,3 +259,26 @@ func TestTuples_Fields(t *testing.T) {
 	assert.Equal(t, map[string]interface{}{"a": 123, "b": 456},
 		ctxd.Tuples{"a", 123, "b", 456}.Fields()) // All good.
 }
+
+func TestNewMulti(t *testing.T) {
+	errPrimary := errors.New("failed")
+	errSecondary1 := ctxd.SentinelError("miserably")
+	errSecondary2 := ctxd.SentinelError("hopelessly")
+	errSecondary3 := ctxd.SentinelError("deadly")
+
+	err := ctxd.MultiError(fmt.Errorf("oops: %w", errPrimary), errSecondary1, errSecondary2)
+
+	assert.True(t, errors.Is(err, errPrimary))
+	assert.True(t, errors.Is(err, errSecondary1))
+	assert.True(t, errors.Is(err, errSecondary2))
+	assert.False(t, errors.Is(err, errSecondary3))
+
+	// Labels do not implicitly contribute to error message.
+	assert.Equal(t, "oops: failed", err.Error())
+
+	// If there are two matches, only first is returned.
+	var errSentinel ctxd.SentinelError
+
+	assert.True(t, errors.As(err, &errSentinel))
+	assert.Equal(t, "miserably", string(errSentinel))
+}
diff --git a/go.mod b/go.mod
index 1d8e1a7..85c4f21 100644
--- a/go.mod
+++ b/go.mod
@@ -3,13 +3,13 @@ module github.com/bool64/ctxd
 go 1.17
 
 require (
-	github.com/bool64/dev v0.2.5
-	github.com/stretchr/testify v1.7.1
-	github.com/swaggest/usecase v1.1.2
+	github.com/bool64/dev v0.2.22
+	github.com/stretchr/testify v1.8.0
+	github.com/swaggest/usecase v1.2.0
 )
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
diff --git a/go.sum b/go.sum
index 7a4a08c..f391c0d 100644
--- a/go.sum
+++ b/go.sum
@@ -1,20 +1,20 @@
-github.com/bool64/dev v0.2.5 h1:H0bylghwcjDBBhEwSFTjArEO9Dr8cCaB54QSOF7esOA=
-github.com/bool64/dev v0.2.5/go.mod h1:cTHiTDNc8EewrQPy3p1obNilpMpdmlUesDkFTF2zRWU=
+github.com/bool64/dev v0.2.20/go.mod h1:iJbh1y/HkunEPhgebWRNcs8wfGq7sjvJ6W5iabL8ACg=
+github.com/bool64/dev v0.2.22 h1:YJFKBRKplkt+0Emq/5Xk1Z5QRmMNzc1UOJkR3rxJksA=
+github.com/bool64/dev v0.2.22/go.mod h1:iJbh1y/HkunEPhgebWRNcs8wfGq7sjvJ6W5iabL8ACg=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/swaggest/usecase v1.1.2 h1:2LfuSyjYtPtpHnxqPwV87/eunbhGBC5HKdRp8/fINBk=
-github.com/swaggest/usecase v1.1.2/go.mod h1:abZWuMFYujaeLDODqRySJZpWD/ugsnE3Wj9K6jUeCjo=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
+github.com/swaggest/usecase v1.2.0 h1:cHVFqxIbHfyTXp02JmWXk+ZADaSa87UZP+b3qL5Nz90=
+github.com/swaggest/usecase v1.2.0/go.mod h1:oc5+QoAxG3Et5Gl9lRXgEOm00l4VN9gdVQSMIa5EeLY=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=