diff --git a/.circleci/config.yml b/.circleci/config.yml
new file mode 100644
index 0000000..225195d
--- /dev/null
+++ b/.circleci/config.yml
@@ -0,0 +1,19 @@
+version: 2
+jobs:
+  build:
+    docker:
+    - image: quay.io/cybozu/golang:1.11-bionic
+    working_directory: /work
+    steps:
+    - checkout
+    - run: test -z "$(gofmt -s -l . | grep -v '^vendor' | tee /dev/stderr)"
+    - run: golint -set_exit_status .
+    - run: go build ./...
+    - run: go test -race -v ./...
+    - run: go vet ./...
+
+workflows:
+  version: 2
+  main:
+    jobs:
+      - build
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 99f7a34..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-sudo: false
-language: go
-go:
-  - stable
-  - master
-
-before_install:
-  - go get github.com/golang/lint/golint
-
-script:
-  - go install ./...
-  - go test -v ./...
-  - go vet -x ./...
-  - $HOME/gopath/bin/golint -set_exit_status -min_confidence 0.81 ./...
diff --git a/cmd/transocks/main.go b/cmd/transocks/main.go
index 2b0cbc8..ad39070 100644
--- a/cmd/transocks/main.go
+++ b/cmd/transocks/main.go
@@ -7,15 +7,15 @@ import (
 	"net/url"
 
 	"github.com/BurntSushi/toml"
-	"github.com/cybozu-go/cmd"
 	"github.com/cybozu-go/log"
 	"github.com/cybozu-go/transocks"
+	"github.com/cybozu-go/well"
 )
 
 type tomlConfig struct {
-	Listen   string        `toml:"listen"`
-	ProxyURL string        `toml:"proxy_url"`
-	Log      cmd.LogConfig `toml:"log"`
+	Listen   string         `toml:"listen"`
+	ProxyURL string         `toml:"proxy_url"`
+	Log      well.LogConfig `toml:"log"`
 }
 
 const (
@@ -65,8 +65,8 @@ func serve(lns []net.Listener, c *transocks.Config) {
 	for _, ln := range lns {
 		s.Serve(ln)
 	}
-	err = cmd.Wait()
-	if err != nil && !cmd.IsSignaled(err) {
+	err = well.Wait()
+	if err != nil && !well.IsSignaled(err) {
 		log.ErrorExit(err)
 	}
 }
@@ -79,7 +79,7 @@ func main() {
 		log.ErrorExit(err)
 	}
 
-	g := &cmd.Graceful{
+	g := &well.Graceful{
 		Listen: func() ([]net.Listener, error) {
 			return transocks.Listeners(c)
 		},
@@ -89,8 +89,8 @@ func main() {
 	}
 	g.Run()
 
-	err = cmd.Wait()
-	if err != nil && !cmd.IsSignaled(err) {
+	err = well.Wait()
+	if err != nil && !well.IsSignaled(err) {
 		log.ErrorExit(err)
 	}
 }
diff --git a/config.go b/config.go
index 8ac1415..62e8aea 100644
--- a/config.go
+++ b/config.go
@@ -7,8 +7,8 @@ import (
 	"net/url"
 	"time"
 
-	"github.com/cybozu-go/cmd"
 	"github.com/cybozu-go/log"
+	"github.com/cybozu-go/well"
 )
 
 const (
@@ -58,9 +58,9 @@ type Config struct {
 	// If nil, the default logger is used.
 	Logger *log.Logger
 
-	// Env can be used to specify a cmd.Environment on which the server runs.
+	// Env can be used to specify a well.Environment on which the server runs.
 	// If nil, the server will run on the global environment.
-	Env *cmd.Environment
+	Env *well.Environment
 }
 
 // NewConfig creates and initializes a new Config.
diff --git a/defs_linux.go b/defs_linux.go
new file mode 100644
index 0000000..ffde475
--- /dev/null
+++ b/defs_linux.go
@@ -0,0 +1,12 @@
+// Code generated by hand.  DO NOT EDIT.
+// +build linux
+
+package transocks
+
+const (
+	// SO_ORIGINAL_DST is a Linux getsockopt optname.
+	SO_ORIGINAL_DST = 80
+
+	// IP6T_SO_ORIGINAL_DST a Linux getsockopt optname.
+	IP6T_SO_ORIGINAL_DST = 80
+)
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..0554be2
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,9 @@
+module github.com/cybozu-go/transocks
+
+require (
+	github.com/BurntSushi/toml v0.3.1
+	github.com/cybozu-go/log v1.5.0
+	github.com/cybozu-go/netutil v1.2.0
+	github.com/cybozu-go/well v1.8.1
+	golang.org/x/net v0.0.0-20180911220305-26e67e76b6c3
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..b35dfc8
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,47 @@
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
+github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/cybozu-go/log v1.5.0 h1:cjLr+pNga4NL5sj5vnnG00xKmKXSWx0grQQ4LnV1Ris=
+github.com/cybozu-go/log v1.5.0/go.mod h1:zpfovuCgUx+a/ErvQrThoT+/z1RVQoLDOf95wkBeRiw=
+github.com/cybozu-go/netutil v1.2.0 h1:UBO0+hB43zd5mIXRfD195eBMHvgWlHP2mYuQ2F5Yxtg=
+github.com/cybozu-go/netutil v1.2.0/go.mod h1:Wx92iF1dPrtuSzLUMEidtrKTFiDWpLcsYvbQ1lHSmxY=
+github.com/cybozu-go/well v1.8.1 h1:YlEPreiDBI+KxE5rcAkkaB5j/Iyow6nIVmUpq3u5DYQ=
+github.com/cybozu-go/well v1.8.1/go.mod h1:9PK1AltjltFwZBtTWVXnCJ0fIeZMxGovYfLmCcZxQog=
+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/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=
+github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
+github.com/hashicorp/hcl v1.0.0 h1:0Anlzjpi4vEasTeNFn2mLJgTSwt0+6sfsiTG8qcWGx4=
+github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
+github.com/magiconair/properties v1.8.0 h1:LLgXmsheXeRoUOBOjtwPQCWIYqM/LU1ayDtDePerRcY=
+github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
+github.com/mitchellh/mapstructure v1.0.0 h1:vVpGvMXJPqSDh2VYHF7gsfQj8Ncx+Xw5Y1KHeTRY+7I=
+github.com/mitchellh/mapstructure v1.0.0/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
+github.com/pelletier/go-toml v1.2.0 h1:T5zMGML61Wp+FlcbWjRDT7yAxhJNAiPPLOFECq181zc=
+github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
+github.com/pkg/errors v0.8.0 h1:WdK/asTD0HN+q6hsWO3/vpuAkAr+tw6aNJNDFFf0+qw=
+github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+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/spf13/afero v1.1.2 h1:m8/z1t7/fwjysjQRYbP0RD+bUIF/8tJwPdEZsI83ACI=
+github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
+github.com/spf13/cast v1.2.0 h1:HHl1DSRbEQN2i8tJmtS6ViPyHx35+p51amrdsiTCrkg=
+github.com/spf13/cast v1.2.0/go.mod h1:r2rcYCSwa1IExKTDiTfzaxqT2FNHs8hODu4LnUfgKEg=
+github.com/spf13/jwalterweatherman v1.0.0 h1:XHEdyB+EcvlqZamSM4ZOMGlc93t6AcsBEu9Gc1vn7yk=
+github.com/spf13/jwalterweatherman v1.0.0/go.mod h1:cQK4TGJAtQXfYWX+Ddv3mKDzgVb68N+wFjFa4jdeBTo=
+github.com/spf13/pflag v1.0.2/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
+github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
+github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
+github.com/spf13/viper v1.2.1 h1:bIcUwXqLseLF3BDAZduuNfekWG87ibtFxi59Bq+oI9M=
+github.com/spf13/viper v1.2.1/go.mod h1:P4AexN0a+C9tGAnUFNwDMYYZv3pjFuvmeiMyKRaNVlI=
+github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+golang.org/x/net v0.0.0-20180911220305-26e67e76b6c3 h1:czFLhve3vsQetD6JOJ8NZZvGQIXlnN3/yXxbT6/awxI=
+golang.org/x/net v0.0.0-20180911220305-26e67e76b6c3/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/sys v0.0.0-20180906133057-8cf3aee42992 h1:BH3eQWeGbwRU2+wxxuuPOdFBmaiBH81O8BugSjHeTFg=
+golang.org/x/sys v0.0.0-20180906133057-8cf3aee42992/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+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 v2.2.1 h1:mUhvW9EsL+naU5Q3cakzfE91YhliOondGd6ZrsDBHQE=
+gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
diff --git a/original_dst_linux.go b/original_dst_linux.go
index 473dea4..cc9bbfb 100644
--- a/original_dst_linux.go
+++ b/original_dst_linux.go
@@ -9,14 +9,6 @@ import (
 	"unsafe"
 )
 
-const (
-	// SO_ORIGINAL_DST is a Linux getsockopt optname.
-	SO_ORIGINAL_DST = 80
-
-	// IP6T_SO_ORIGINAL_DST a Linux getsockopt optname.
-	IP6T_SO_ORIGINAL_DST = 80
-)
-
 func getsockopt(s int, level int, optname int, optval unsafe.Pointer, optlen *uint32) (err error) {
 	_, _, e := syscall.Syscall6(
 		syscall.SYS_GETSOCKOPT, uintptr(s), uintptr(level), uintptr(optname),
diff --git a/server.go b/server.go
index ae7e1b4..35e534e 100644
--- a/server.go
+++ b/server.go
@@ -7,9 +7,9 @@ import (
 	"sync"
 	"time"
 
-	"github.com/cybozu-go/cmd"
 	"github.com/cybozu-go/log"
 	"github.com/cybozu-go/netutil"
+	"github.com/cybozu-go/well"
 	"golang.org/x/net/proxy"
 )
 
@@ -29,7 +29,7 @@ func Listeners(c *Config) ([]net.Listener, error) {
 
 // Server provides transparent proxy server functions.
 type Server struct {
-	cmd.Server
+	well.Server
 	mode   Mode
 	logger *log.Logger
 	dialer proxy.Dialer
@@ -60,7 +60,7 @@ func NewServer(c *Config) (*Server, error) {
 	}
 
 	s := &Server{
-		Server: cmd.Server{
+		Server: well.Server{
 			ShutdownTimeout: c.ShutdownTimeout,
 			Env:             c.Env,
 		},
@@ -86,7 +86,7 @@ func (s *Server) handleConnection(ctx context.Context, conn net.Conn) {
 		return
 	}
 
-	fields := cmd.FieldsFromContext(ctx)
+	fields := well.FieldsFromContext(ctx)
 	fields[log.FnType] = "access"
 	fields["client_addr"] = conn.RemoteAddr().String()
 
@@ -117,7 +117,7 @@ func (s *Server) handleConnection(ctx context.Context, conn net.Conn) {
 
 	// do proxy
 	st := time.Now()
-	env := cmd.NewEnvironment(ctx)
+	env := well.NewEnvironment(ctx)
 	env.Go(func(ctx context.Context) error {
 		buf := s.pool.Get().([]byte)
 		_, err := io.CopyBuffer(destConn, tc, buf)
@@ -141,7 +141,7 @@ func (s *Server) handleConnection(ctx context.Context, conn net.Conn) {
 	env.Stop()
 	err = env.Wait()
 
-	fields = cmd.FieldsFromContext(ctx)
+	fields = well.FieldsFromContext(ctx)
 	fields["elapsed"] = time.Since(st).Seconds()
 	if err != nil {
 		fields[log.FnError] = err.Error()