diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..b1e20fbe
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,68 @@
+name: Continuous integration
+
+on: [push, pull_request]
+
+defaults:
+  run:
+    shell: bash
+
+jobs:
+  test:
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        go: [1.16.x, 1.15.x, 1.14.x, 1.13.x]
+    name: Go ${{ matrix.go }} tests @ ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - name: Install Linux dependencies
+        if: startsWith(matrix.os, 'ubuntu-')
+        run: |
+          sudo apt-get update
+          sudo apt-get install -yq librocksdb-dev
+
+      - name: Install MacOS dependencies
+        if: startsWith(matrix.os, 'macos-')
+        run: |
+          brew update
+          brew install rocksdb
+
+      - name: Install Golang ${{ matrix.go }}
+        id: install-golang
+        uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go }}
+      - run: go version
+
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Cache Golang modules
+        uses: actions/cache@v2
+        with:
+          path: ~/go/pkg/mod
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+          restore-keys: |
+            ${{ runner.os }}-go-
+
+      - name: Test v5
+        if: startsWith(matrix.os, 'ubuntu-')
+        run: go test -v
+
+      - name: Test v6.16 or later
+        if: startsWith(matrix.os, 'macos-')
+        run: go test -v -tags rocksdb_6_16
+
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - name: Install Linux dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -yq librocksdb-dev
+      - uses: actions/checkout@v2
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v2
+        with:
+          version: latest
diff --git a/.gitignore b/.gitignore
index 485dee64..3ce5adbb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 .idea
+vendor
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 00000000..2babb434
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,56 @@
+# options for analysis running
+run:
+  # default concurrency is a available CPU number
+  concurrency: 4
+
+  # timeout for analysis, e.g. 30s, 5m, default is 1m
+  timeout: 20m
+
+  # exit code when at least one issue was found, default is 1
+  issues-exit-code: 1
+
+  # include test files or not, default is true
+  tests: true
+
+  # default is true. Enables skipping of directories:
+  #   vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
+  skip-dirs-use-default: true
+
+  # which dirs to skip: they won't be analyzed;
+  # can use regexp here: generated.*, regexp is applied on full path;
+  # default value is empty list, but next dirs are always skipped independently
+  # from this option's value:
+  #   	vendor$, third_party$, testdata$, examples$, Godeps$, builtin$
+  #  skip-dirs:
+  #    - ^test.*
+
+  # by default isn't set. If set we pass it to "go list -mod={option}". From "go help modules":
+  # If invoked with -mod=readonly, the go command is disallowed from the implicit
+  # automatic updating of go.mod described above. Instead, it fails when any changes
+  # to go.mod are needed. This setting is most useful to check that go.mod does
+  # not need updates, such as in a continuous integration and testing system.
+  # If invoked with -mod=vendor, the go command assumes that the vendor
+  # directory holds the correct copies of dependencies and ignores
+  # the dependency descriptions in go.mod.
+  modules-download-mode: readonly
+
+  # which files to skip: they will be analyzed, but issues from them
+  # won't be reported. Default value is empty list, but there is
+  # no need to include all autogenerated files, we confidently recognize
+  # autogenerated files. If it's not please let us know.
+  # skip-files:
+  #  - ".*\\.my\\.go$"
+  #  - lib/bad.go
+
+# all available settings of specific linters
+linters-settings:
+  govet:
+    enable:
+      - nilness
+  misspell:
+    # Correct spellings using locale preferences for US or UK.
+    # Default is to use a neutral variety of English.
+    # Setting locale to US will correct the British spelling of 'colour' to 'color'.
+    # locale: US
+    ignore-words:
+      - rela # This is for elf.SHT_RELA
diff --git a/.travis.yml b/.travis.yml
index 9b331467..8e27ad7c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,8 +1,10 @@
 dist: xenial
 language: go
 go:
-  - 1.12.x
   - 1.13.x
+  - 1.14.x
+  - 1.15.x
+  - 1.16.x
   - tip
 
 before_install:
@@ -24,10 +26,10 @@ install:
   - sudo cp --preserve=links ./librocksdb.* /usr/lib/
   - sudo cp -r ./include/rocksdb/ /usr/include/
   - popd
-  - go get -t ./...
+  - go get -t -tags rocksdb_6_16 ./...
 
 script:
-  - go test -v ./
+  - go test -v -tags rocksdb_6_16 ./
 
 notifications:
   email:
diff --git a/checkpoint_test.go b/checkpoint_test.go
index 1ea10fdb..d90d47ed 100644
--- a/checkpoint_test.go
+++ b/checkpoint_test.go
@@ -41,8 +41,8 @@ func TestCheckpoint(t *testing.T) {
 	opts := NewDefaultOptions()
 	opts.SetCreateIfMissing(true)
 	dbCheck, err = OpenDb(opts, dir)
-	defer dbCheck.Close()
 	ensure.Nil(t, err)
+	defer dbCheck.Close()
 
 	// test keys
 	var value *Slice
diff --git a/db.go b/db.go
index 64735c61..5764f7c0 100755
--- a/db.go
+++ b/db.go
@@ -577,89 +577,6 @@ func (db *DB) DropColumnFamily(c *ColumnFamilyHandle) error {
 	return nil
 }
 
-// GetApproximateSizes returns the approximate number of bytes of file system
-// space used by one or more key ranges.
-//
-// The keys counted will begin at Range.Start and end on the key before
-// Range.Limit.
-func (db *DB) GetApproximateSizes(ranges []Range) []uint64 {
-	sizes := make([]uint64, len(ranges))
-	if len(ranges) == 0 {
-		return sizes
-	}
-
-	cStarts := make([]*C.char, len(ranges))
-	cLimits := make([]*C.char, len(ranges))
-	cStartLens := make([]C.size_t, len(ranges))
-	cLimitLens := make([]C.size_t, len(ranges))
-	for i, r := range ranges {
-		cStarts[i] = (*C.char)(C.CBytes(r.Start))
-		cStartLens[i] = C.size_t(len(r.Start))
-		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
-		cLimitLens[i] = C.size_t(len(r.Limit))
-	}
-
-	defer func() {
-		for i := range ranges {
-			C.free(unsafe.Pointer(cStarts[i]))
-			C.free(unsafe.Pointer(cLimits[i]))
-		}
-	}()
-
-	C.rocksdb_approximate_sizes(
-		db.c,
-		C.int(len(ranges)),
-		&cStarts[0],
-		&cStartLens[0],
-		&cLimits[0],
-		&cLimitLens[0],
-		(*C.uint64_t)(&sizes[0]))
-
-	return sizes
-}
-
-// GetApproximateSizesCF returns the approximate number of bytes of file system
-// space used by one or more key ranges in the column family.
-//
-// The keys counted will begin at Range.Start and end on the key before
-// Range.Limit.
-func (db *DB) GetApproximateSizesCF(cf *ColumnFamilyHandle, ranges []Range) []uint64 {
-	sizes := make([]uint64, len(ranges))
-	if len(ranges) == 0 {
-		return sizes
-	}
-
-	cStarts := make([]*C.char, len(ranges))
-	cLimits := make([]*C.char, len(ranges))
-	cStartLens := make([]C.size_t, len(ranges))
-	cLimitLens := make([]C.size_t, len(ranges))
-	for i, r := range ranges {
-		cStarts[i] = (*C.char)(C.CBytes(r.Start))
-		cStartLens[i] = C.size_t(len(r.Start))
-		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
-		cLimitLens[i] = C.size_t(len(r.Limit))
-	}
-
-	defer func() {
-		for i := range ranges {
-			C.free(unsafe.Pointer(cStarts[i]))
-			C.free(unsafe.Pointer(cLimits[i]))
-		}
-	}()
-
-	C.rocksdb_approximate_sizes_cf(
-		db.c,
-		cf.c,
-		C.int(len(ranges)),
-		&cStarts[0],
-		&cStartLens[0],
-		&cLimits[0],
-		&cLimitLens[0],
-		(*C.uint64_t)(&sizes[0]))
-
-	return sizes
-}
-
 // SetOptions dynamically changes options through the SetOptions API.
 func (db *DB) SetOptions(keys, values []string) error {
 	num_keys := len(keys)
diff --git a/db_6.go b/db_6.go
new file mode 100644
index 00000000..e599f93f
--- /dev/null
+++ b/db_6.go
@@ -0,0 +1,91 @@
+// +build !rocksdb_6_16
+
+package gorocksdb
+
+// #include <stdlib.h>
+// #include "rocksdb/c.h"
+import "C"
+import "unsafe"
+
+// GetApproximateSizes returns the approximate number of bytes of file system
+// space used by one or more key ranges.
+//
+// The keys counted will begin at Range.Start and end on the key before
+// Range.Limit.
+func (db *DB) GetApproximateSizes(ranges []Range) []uint64 {
+	sizes := make([]uint64, len(ranges))
+	if len(ranges) == 0 {
+		return sizes
+	}
+
+	cStarts := make([]*C.char, len(ranges))
+	cLimits := make([]*C.char, len(ranges))
+	cStartLens := make([]C.size_t, len(ranges))
+	cLimitLens := make([]C.size_t, len(ranges))
+	for i, r := range ranges {
+		cStarts[i] = (*C.char)(C.CBytes(r.Start))
+		cStartLens[i] = C.size_t(len(r.Start))
+		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
+		cLimitLens[i] = C.size_t(len(r.Limit))
+	}
+
+	defer func() {
+		for i := range ranges {
+			C.free(unsafe.Pointer(cStarts[i]))
+			C.free(unsafe.Pointer(cLimits[i]))
+		}
+	}()
+
+	C.rocksdb_approximate_sizes(
+		db.c,
+		C.int(len(ranges)),
+		&cStarts[0],
+		&cStartLens[0],
+		&cLimits[0],
+		&cLimitLens[0],
+		(*C.uint64_t)(&sizes[0]))
+
+	return sizes
+}
+
+// GetApproximateSizesCF returns the approximate number of bytes of file system
+// space used by one or more key ranges in the column family.
+//
+// The keys counted will begin at Range.Start and end on the key before
+// Range.Limit.
+func (db *DB) GetApproximateSizesCF(cf *ColumnFamilyHandle, ranges []Range) []uint64 {
+	sizes := make([]uint64, len(ranges))
+	if len(ranges) == 0 {
+		return sizes
+	}
+
+	cStarts := make([]*C.char, len(ranges))
+	cLimits := make([]*C.char, len(ranges))
+	cStartLens := make([]C.size_t, len(ranges))
+	cLimitLens := make([]C.size_t, len(ranges))
+	for i, r := range ranges {
+		cStarts[i] = (*C.char)(C.CBytes(r.Start))
+		cStartLens[i] = C.size_t(len(r.Start))
+		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
+		cLimitLens[i] = C.size_t(len(r.Limit))
+	}
+
+	defer func() {
+		for i := range ranges {
+			C.free(unsafe.Pointer(cStarts[i]))
+			C.free(unsafe.Pointer(cLimits[i]))
+		}
+	}()
+
+	C.rocksdb_approximate_sizes_cf(
+		db.c,
+		cf.c,
+		C.int(len(ranges)),
+		&cStarts[0],
+		&cStartLens[0],
+		&cLimits[0],
+		&cLimitLens[0],
+		(*C.uint64_t)(&sizes[0]))
+
+	return sizes
+}
diff --git a/db_6_16.go b/db_6_16.go
new file mode 100644
index 00000000..756f9fcf
--- /dev/null
+++ b/db_6_16.go
@@ -0,0 +1,108 @@
+// +build rocksdb_6_16
+
+package gorocksdb
+
+// #include <stdlib.h>
+// #include "rocksdb/c.h"
+import "C"
+import (
+	"errors"
+	"unsafe"
+)
+
+// GetApproximateSizes returns the approximate number of bytes of file system
+// space used by one or more key ranges.
+//
+// The keys counted will begin at Range.Start and end on the key before
+// Range.Limit.
+func (db *DB) GetApproximateSizes(ranges []Range) (sizes []uint64, err error) {
+	var cErr *C.char
+	sizes = make([]uint64, len(ranges))
+	if len(ranges) == 0 {
+		return
+	}
+
+	cStarts := make([]*C.char, len(ranges))
+	cLimits := make([]*C.char, len(ranges))
+	cStartLens := make([]C.size_t, len(ranges))
+	cLimitLens := make([]C.size_t, len(ranges))
+	for i, r := range ranges {
+		cStarts[i] = (*C.char)(C.CBytes(r.Start))
+		cStartLens[i] = C.size_t(len(r.Start))
+		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
+		cLimitLens[i] = C.size_t(len(r.Limit))
+	}
+
+	defer func() {
+		for i := range ranges {
+			C.free(unsafe.Pointer(cStarts[i]))
+			C.free(unsafe.Pointer(cLimits[i]))
+		}
+	}()
+
+	C.rocksdb_approximate_sizes(
+		db.c,
+		C.int(len(ranges)),
+		&cStarts[0],
+		&cStartLens[0],
+		&cLimits[0],
+		&cLimitLens[0],
+		(*C.uint64_t)(&sizes[0]),
+		&cErr,
+	)
+	if cErr != nil {
+		defer C.rocksdb_free(unsafe.Pointer(cErr))
+		err = errors.New(C.GoString(cErr))
+	}
+
+	return
+}
+
+// GetApproximateSizesCF returns the approximate number of bytes of file system
+// space used by one or more key ranges in the column family.
+//
+// The keys counted will begin at Range.Start and end on the key before
+// Range.Limit.
+func (db *DB) GetApproximateSizesCF(cf *ColumnFamilyHandle, ranges []Range) (sizes []uint64, err error) {
+	var cErr *C.char
+	sizes = make([]uint64, len(ranges))
+	if len(ranges) == 0 {
+		return
+	}
+
+	cStarts := make([]*C.char, len(ranges))
+	cLimits := make([]*C.char, len(ranges))
+	cStartLens := make([]C.size_t, len(ranges))
+	cLimitLens := make([]C.size_t, len(ranges))
+	for i, r := range ranges {
+		cStarts[i] = (*C.char)(C.CBytes(r.Start))
+		cStartLens[i] = C.size_t(len(r.Start))
+		cLimits[i] = (*C.char)(C.CBytes(r.Limit))
+		cLimitLens[i] = C.size_t(len(r.Limit))
+	}
+
+	defer func() {
+		for i := range ranges {
+			C.free(unsafe.Pointer(cStarts[i]))
+			C.free(unsafe.Pointer(cLimits[i]))
+		}
+	}()
+
+	C.rocksdb_approximate_sizes_cf(
+		db.c,
+		cf.c,
+		C.int(len(ranges)),
+		&cStarts[0],
+		&cStartLens[0],
+		&cLimits[0],
+		&cLimitLens[0],
+		(*C.uint64_t)(&sizes[0]),
+		&cErr,
+	)
+	if cErr != nil {
+		defer C.rocksdb_free(unsafe.Pointer(cErr))
+		err = errors.New(C.GoString(cErr))
+	}
+
+	return
+}
diff --git a/db_6_16_test.go b/db_6_16_test.go
new file mode 100644
index 00000000..6deace37
--- /dev/null
+++ b/db_6_16_test.go
@@ -0,0 +1,54 @@
+// +build rocksdb_6_16
+
+package gorocksdb
+
+import (
+	"testing"
+
+	"github.com/facebookgo/ensure"
+)
+
+func TestDBGetApproximateSizes(t *testing.T) {
+	db := newTestDB(t, "TestDBGetApproximateSizes", nil)
+	defer db.Close()
+
+	// no ranges
+	sizes, err := db.GetApproximateSizes(nil)
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, len(sizes), 0)
+
+	// range will nil start and limit
+	sizes, err = db.GetApproximateSizes([]Range{{Start: nil, Limit: nil}})
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, sizes, []uint64{0})
+
+	// valid range
+	sizes, err = db.GetApproximateSizes([]Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, sizes, []uint64{0})
+}
+
+func TestDBGetApproximateSizesCF(t *testing.T) {
+	db := newTestDB(t, "TestDBGetApproximateSizesCF", nil)
+	defer db.Close()
+
+	o := NewDefaultOptions()
+
+	cf, err := db.CreateColumnFamily(o, "other")
+	ensure.Nil(t, err)
+
+	// no ranges
+	sizes, err := db.GetApproximateSizesCF(cf, nil)
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, len(sizes), 0)
+
+	// range will nil start and limit
+	sizes, err = db.GetApproximateSizesCF(cf, []Range{{Start: nil, Limit: nil}})
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, sizes, []uint64{0})
+
+	// valid range
+	sizes, err = db.GetApproximateSizesCF(cf, []Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
+	ensure.Nil(t, err)
+	ensure.DeepEqual(t, sizes, []uint64{0})
+}
diff --git a/db_6_test.go b/db_6_test.go
new file mode 100644
index 00000000..3c5ca62b
--- /dev/null
+++ b/db_6_test.go
@@ -0,0 +1,48 @@
+// +build !rocksdb_6_16
+
+package gorocksdb
+
+import (
+	"testing"
+
+	"github.com/facebookgo/ensure"
+)
+
+func TestDBGetApproximateSizes(t *testing.T) {
+	db := newTestDB(t, "TestDBGetApproximateSizes", nil)
+	defer db.Close()
+
+	// no ranges
+	sizes := db.GetApproximateSizes(nil)
+	ensure.DeepEqual(t, len(sizes), 0)
+
+	// range will nil start and limit
+	sizes = db.GetApproximateSizes([]Range{{Start: nil, Limit: nil}})
+	ensure.DeepEqual(t, sizes, []uint64{0})
+
+	// valid range
+	sizes = db.GetApproximateSizes([]Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
+	ensure.DeepEqual(t, sizes, []uint64{0})
+}
+
+func TestDBGetApproximateSizesCF(t *testing.T) {
+	db := newTestDB(t, "TestDBGetApproximateSizesCF", nil)
+	defer db.Close()
+
+	o := NewDefaultOptions()
+
+	cf, err := db.CreateColumnFamily(o, "other")
+	ensure.Nil(t, err)
+
+	// no ranges
+	sizes := db.GetApproximateSizesCF(cf, nil)
+	ensure.DeepEqual(t, len(sizes), 0)
+
+	// range will nil start and limit
+	sizes = db.GetApproximateSizesCF(cf, []Range{{Start: nil, Limit: nil}})
+	ensure.DeepEqual(t, sizes, []uint64{0})
+
+	// valid range
+	sizes = db.GetApproximateSizesCF(cf, []Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
+	ensure.DeepEqual(t, sizes, []uint64{0})
+}
diff --git a/db_test.go b/db_test.go
index 4ccc7aa8..87696d57 100755
--- a/db_test.go
+++ b/db_test.go
@@ -204,42 +204,3 @@ func TestDBMultiGet(t *testing.T) {
 	ensure.DeepEqual(t, values[2].Data(), givenVal2)
 	ensure.DeepEqual(t, values[3].Data(), givenVal3)
 }
-
-func TestDBGetApproximateSizes(t *testing.T) {
-	db := newTestDB(t, "TestDBGetApproximateSizes", nil)
-	defer db.Close()
-
-	// no ranges
-	sizes := db.GetApproximateSizes(nil)
-	ensure.DeepEqual(t, len(sizes), 0)
-
-	// range will nil start and limit
-	sizes = db.GetApproximateSizes([]Range{{Start: nil, Limit: nil}})
-	ensure.DeepEqual(t, sizes, []uint64{0})
-
-	// valid range
-	sizes = db.GetApproximateSizes([]Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
-	ensure.DeepEqual(t, sizes, []uint64{0})
-}
-
-func TestDBGetApproximateSizesCF(t *testing.T) {
-	db := newTestDB(t, "TestDBGetApproximateSizesCF", nil)
-	defer db.Close()
-
-	o := NewDefaultOptions()
-
-	cf, err := db.CreateColumnFamily(o, "other")
-	ensure.Nil(t, err)
-
-	// no ranges
-	sizes := db.GetApproximateSizesCF(cf, nil)
-	ensure.DeepEqual(t, len(sizes), 0)
-
-	// range will nil start and limit
-	sizes = db.GetApproximateSizesCF(cf, []Range{{Start: nil, Limit: nil}})
-	ensure.DeepEqual(t, sizes, []uint64{0})
-
-	// valid range
-	sizes = db.GetApproximateSizesCF(cf, []Range{{Start: []byte{0x00}, Limit: []byte{0xFF}}})
-	ensure.DeepEqual(t, sizes, []uint64{0})
-}
diff --git a/go.mod b/go.mod
new file mode 100644
index 00000000..b0912f25
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,10 @@
+module github.com/tecbot/gorocksdb
+
+go 1.13
+
+require (
+	github.com/facebookgo/ensure v0.0.0-20200202191622-63f1cf65ac4c
+	github.com/facebookgo/stack v0.0.0-20160209184415-751773369052 // indirect
+	github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4 // indirect
+	github.com/stretchr/testify v1.7.0
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 00000000..35ffeaf5
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,16 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/facebookgo/ensure v0.0.0-20200202191622-63f1cf65ac4c h1:8ISkoahWXwZR41ois5lSJBSVw4D0OV19Ht/JSTzvSv0=
+github.com/facebookgo/ensure v0.0.0-20200202191622-63f1cf65ac4c/go.mod h1:Yg+htXGokKKdzcwhuNDwVvN+uBxDGXJ7G/VN1d8fa64=
+github.com/facebookgo/stack v0.0.0-20160209184415-751773369052 h1:JWuenKqqX8nojtoVVWjGfOF9635RETekkoH6Cc9SX0A=
+github.com/facebookgo/stack v0.0.0-20160209184415-751773369052/go.mod h1:UbMTZqLaRiH3MsBH8va0n7s1pQYcu3uTb8G4tygF4Zg=
+github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4 h1:7HZCaLC5+BZpmbhCOZJ293Lz68O7PYrF2EzeiFMwCLk=
+github.com/facebookgo/subset v0.0.0-20200203212716-c811ad88dec4/go.mod h1:5tD+neXqOorC30/tWg0LCSkrqj/AR6gu8yY8/fpw1q0=
+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 v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/slice_transform_test.go b/slice_transform_test.go
index d60c7326..28664f1d 100644
--- a/slice_transform_test.go
+++ b/slice_transform_test.go
@@ -43,7 +43,7 @@ func TestNewNoopPrefixTransform(t *testing.T) {
 }
 
 type testSliceTransform struct {
-	initiated bool
+	// initiated bool
 }
 
 func (st *testSliceTransform) Name() string                { return "gorocksdb.test" }
diff --git a/util.go b/util.go
index b6637ec3..f994d3f8 100644
--- a/util.go
+++ b/util.go
@@ -52,10 +52,10 @@ func cByteSlice(b []byte) *C.char {
 }
 
 // stringToChar returns *C.char from string.
-func stringToChar(s string) *C.char {
-	ptrStr := (*reflect.StringHeader)(unsafe.Pointer(&s))
-	return (*C.char)(unsafe.Pointer(ptrStr.Data))
-}
+// func stringToChar(s string) *C.char {
+// 	ptrStr := (*reflect.StringHeader)(unsafe.Pointer(&s))
+// 	return (*C.char)(unsafe.Pointer(ptrStr.Data))
+// }
 
 // charSlice converts a C array of *char to a []*C.char.
 func charSlice(data **C.char, len C.int) []*C.char {