diff --git a/call_option.go b/call_option.go
index 7b62164..0a17201 100644
--- a/call_option.go
+++ b/call_option.go
@@ -30,37 +30,21 @@
 package gax
 
 import (
-	"math/rand"
-	"time"
-
+	v2 "github.com/googleapis/gax-go/v2"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 )
 
 // CallOption is an option used by Invoke to control behaviors of RPC calls.
 // CallOption works by modifying relevant fields of CallSettings.
-type CallOption interface {
-	// Resolve applies the option by modifying cs.
-	Resolve(cs *CallSettings)
-}
+type CallOption = v2.CallOption
 
 // Retryer is used by Invoke to determine retry behavior.
-type Retryer interface {
-	// Retry reports whether a request should be retriedand how long to pause before retrying
-	// if the previous attempt returned with err. Invoke never calls Retry with nil error.
-	Retry(err error) (pause time.Duration, shouldRetry bool)
-}
-
-type retryerOption func() Retryer
-
-func (o retryerOption) Resolve(s *CallSettings) {
-	s.Retry = o
-}
+type Retryer = v2.Retryer
 
 // WithRetry sets CallSettings.Retry to fn.
 func WithRetry(fn func() Retryer) CallOption {
-	return retryerOption(fn)
+	return v2.WithRetry(fn)
 }
 
 // OnCodes returns a Retryer that retries if and only if
@@ -69,89 +53,17 @@
 //
 // bo is only used for its parameters; each Retryer has its own copy.
 func OnCodes(cc []codes.Code, bo Backoff) Retryer {
-	return &boRetryer{
-		backoff: bo,
-		codes:   append([]codes.Code(nil), cc...),
-	}
-}
-
-type boRetryer struct {
-	backoff Backoff
-	codes   []codes.Code
-}
-
-func (r *boRetryer) Retry(err error) (time.Duration, bool) {
-	st, ok := status.FromError(err)
-	if !ok {
-		return 0, false
-	}
-	c := st.Code()
-	for _, rc := range r.codes {
-		if c == rc {
-			return r.backoff.Pause(), true
-		}
-	}
-	return 0, false
+	return v2.OnCodes(cc, bo)
 }
 
 // Backoff implements exponential backoff.
 // The wait time between retries is a random value between 0 and the "retry envelope".
 // The envelope starts at Initial and increases by the factor of Multiplier every retry,
 // but is capped at Max.
-type Backoff struct {
-	// Initial is the initial value of the retry envelope, defaults to 1 second.
-	Initial time.Duration
-
-	// Max is the maximum value of the retry envelope, defaults to 30 seconds.
-	Max time.Duration
-
-	// Multiplier is the factor by which the retry envelope increases.
-	// It should be greater than 1 and defaults to 2.
-	Multiplier float64
-
-	// cur is the current retry envelope
-	cur time.Duration
-}
-
-func (bo *Backoff) Pause() time.Duration {
-	if bo.Initial == 0 {
-		bo.Initial = time.Second
-	}
-	if bo.cur == 0 {
-		bo.cur = bo.Initial
-	}
-	if bo.Max == 0 {
-		bo.Max = 30 * time.Second
-	}
-	if bo.Multiplier < 1 {
-		bo.Multiplier = 2
-	}
-	// Select a duration between zero and the current max. It might seem counterintuitive to
-	// have so much jitter, but https://www.awsarchitectureblog.com/2015/03/backoff.html
-	// argues that that is the best strategy.
-	d := time.Duration(rand.Int63n(int64(bo.cur)))
-	bo.cur = time.Duration(float64(bo.cur) * bo.Multiplier)
-	if bo.cur > bo.Max {
-		bo.cur = bo.Max
-	}
-	return d
-}
-
-type grpcOpt []grpc.CallOption
-
-func (o grpcOpt) Resolve(s *CallSettings) {
-	s.GRPC = o
-}
+type Backoff = v2.Backoff
 
 func WithGRPCOptions(opt ...grpc.CallOption) CallOption {
-	return grpcOpt(append([]grpc.CallOption(nil), opt...))
+	return v2.WithGRPCOptions(opt...)
 }
 
-type CallSettings struct {
-	// Retry returns a Retryer to be used to control retry logic of a method call.
-	// If Retry is nil or the returned Retryer is nil, the call will not be retried.
-	Retry func() Retryer
-
-	// CallOptions to be forwarded to GRPC.
-	GRPC []grpc.CallOption
-}
+type CallSettings = v2.CallSettings
diff --git a/call_option_test.go b/call_option_test.go
deleted file mode 100644
index 6f81305..0000000
--- a/call_option_test.go
+++ /dev/null
@@ -1,88 +0,0 @@
-// Copyright 2016, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-package gax
-
-import (
-	"testing"
-	"time"
-
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
-)
-
-var _ Retryer = &boRetryer{}
-
-func TestBackofDefault(t *testing.T) {
-	backoff := Backoff{}
-
-	max := []time.Duration{1, 2, 4, 8, 16, 30, 30, 30, 30, 30}
-	for i, m := range max {
-		max[i] = m * time.Second
-	}
-
-	for i, w := range max {
-		if d := backoff.Pause(); d > w {
-			t.Errorf("Backoff duration should be at most %s, got %s", w, d)
-		} else if i < len(max)-1 && backoff.cur != max[i+1] {
-			t.Errorf("current envelope is %s, want %s", backoff.cur, max[i+1])
-		}
-	}
-}
-
-func TestBackoffExponential(t *testing.T) {
-	backoff := Backoff{Initial: 1, Max: 20, Multiplier: 2}
-	want := []time.Duration{1, 2, 4, 8, 16, 20, 20, 20, 20, 20}
-	for _, w := range want {
-		if d := backoff.Pause(); d > w {
-			t.Errorf("Backoff duration should be at most %s, got %s", w, d)
-		}
-	}
-}
-
-func TestOnCodes(t *testing.T) {
-	// Lint errors grpc.Errorf in 1.6. It mistakenly expects the first arg to Errorf to be a string.
-	errf := status.Errorf
-	apiErr := errf(codes.Unavailable, "")
-	tests := []struct {
-		c     []codes.Code
-		retry bool
-	}{
-		{nil, false},
-		{[]codes.Code{codes.DeadlineExceeded}, false},
-		{[]codes.Code{codes.DeadlineExceeded, codes.Unavailable}, true},
-		{[]codes.Code{codes.Unavailable}, true},
-	}
-	for _, tst := range tests {
-		b := OnCodes(tst.c, Backoff{})
-		if _, retry := b.Retry(apiErr); retry != tst.retry {
-			t.Errorf("retriable codes: %v, error: %s, retry: %t, want %t", tst.c, apiErr, retry, tst.retry)
-		}
-	}
-}
diff --git a/gax.go b/gax.go
index 8b2900e..4613b43 100644
--- a/gax.go
+++ b/gax.go
@@ -35,4 +35,4 @@
 // to simplify code generation and to provide more convenient and idiomatic API surfaces.
 package gax
 
-const Version = "2.0.0"
+const Version = "1.0.1"
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..dc69a07
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,6 @@
+module github.com/googleapis/gax-go
+
+require (
+	github.com/googleapis/gax-go/v2 v2.0.2
+	google.golang.org/grpc v1.16.0
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..2fb5cc0
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,28 @@
+cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
+github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
+github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
+github.com/golang/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:tluoj9z5200jBnyusfRPU2LqT6J+DAorxEvtC7LHB+E=
+github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
+github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/googleapis/gax-go/v2 v2.0.2 h1:/rNgUniLy2vDXiK2xyJOcirGpC3G99dtK1NWx26WZ8Y=
+github.com/googleapis/gax-go/v2 v2.0.2/go.mod h1:LLvjysVCY1JZeum8Z6l8qUty8fiNwE08qbEPm1M08qg=
+github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
+golang.org/x/lint v0.0.0-20180702182130-06c8688daad7/go.mod h1:UVdnD1Gm6xHRNCYTkRU2/jEulfH38KcIWyp/GAMgvoE=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d h1:g9qWBGx4puODJTMVyoPrpoxPFgVGd+z1DZwjfRu4d0I=
+golang.org/x/net v0.0.0-20180826012351-8a410e7b638d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
+golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f h1:wMNYb4v58l5UBM7MYRLPG6ZhfOqbKu7X5eyFl8ZhKvA=
+golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20180830151530-49385e6e1522 h1:Ve1ORMCxvRmSXBwJK+t3Oy+V2vRW2OetUQBq4rJIkZE=
+golang.org/x/sys v0.0.0-20180830151530-49385e6e1522/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=
+golang.org/x/tools v0.0.0-20180828015842-6cd1fcedba52/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
+google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
+google.golang.org/grpc v1.16.0 h1:dz5IJGuC2BB7qXR5AyHNwAUBhZscK2xVez7mznh72sY=
+google.golang.org/grpc v1.16.0/go.mod h1:0JHn/cJsOMiMfNA9+DeHDlAU7KAAB5GDlYFpa9MZMio=
+honnef.co/go/tools v0.0.0-20180728063816-88497007e858/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=
diff --git a/header.go b/header.go
index d81455e..2d434c8 100644
--- a/header.go
+++ b/header.go
@@ -1,24 +1,11 @@
 package gax
 
-import "bytes"
+import v2 "github.com/googleapis/gax-go/v2"
 
 // XGoogHeader is for use by the Google Cloud Libraries only.
 //
 // XGoogHeader formats key-value pairs.
 // The resulting string is suitable for x-goog-api-client header.
 func XGoogHeader(keyval ...string) string {
-	if len(keyval) == 0 {
-		return ""
-	}
-	if len(keyval)%2 != 0 {
-		panic("gax.Header: odd argument count")
-	}
-	var buf bytes.Buffer
-	for i := 0; i < len(keyval); i += 2 {
-		buf.WriteByte(' ')
-		buf.WriteString(keyval[i])
-		buf.WriteByte('/')
-		buf.WriteString(keyval[i+1])
-	}
-	return buf.String()[1:]
+	return v2.XGoogHeader(keyval...)
 }
diff --git a/header_test.go b/header_test.go
deleted file mode 100644
index 05d8de6..0000000
--- a/header_test.go
+++ /dev/null
@@ -1,19 +0,0 @@
-package gax
-
-import "testing"
-
-func TestXGoogHeader(t *testing.T) {
-	for _, tst := range []struct {
-		kv   []string
-		want string
-	}{
-		{nil, ""},
-		{[]string{"abc", "def"}, "abc/def"},
-		{[]string{"abc", "def", "xyz", "123", "foo", ""}, "abc/def xyz/123 foo/"},
-	} {
-		got := XGoogHeader(tst.kv...)
-		if got != tst.want {
-			t.Errorf("Header(%q) = %q, want %q", tst.kv, got, tst.want)
-		}
-	}
-}
diff --git a/invoke.go b/invoke.go
index cb5cd2a..c6582c6 100644
--- a/invoke.go
+++ b/invoke.go
@@ -32,58 +32,21 @@
 import (
 	"context"
 	"time"
+
+	v2 "github.com/googleapis/gax-go/v2"
 )
 
 // A user defined call stub.
-type APICall func(context.Context, CallSettings) error
+type APICall = v2.APICall
 
 // Invoke calls the given APICall,
 // performing retries as specified by opts, if any.
 func Invoke(ctx context.Context, call APICall, opts ...CallOption) error {
-	var settings CallSettings
-	for _, opt := range opts {
-		opt.Resolve(&settings)
-	}
-	return invoke(ctx, call, settings, Sleep)
+	return v2.Invoke(ctx, call, opts...)
 }
 
 // Sleep is similar to time.Sleep, but it can be interrupted by ctx.Done() closing.
 // If interrupted, Sleep returns ctx.Err().
 func Sleep(ctx context.Context, d time.Duration) error {
-	t := time.NewTimer(d)
-	select {
-	case <-ctx.Done():
-		t.Stop()
-		return ctx.Err()
-	case <-t.C:
-		return nil
-	}
-}
-
-type sleeper func(ctx context.Context, d time.Duration) error
-
-// invoke implements Invoke, taking an additional sleeper argument for testing.
-func invoke(ctx context.Context, call APICall, settings CallSettings, sp sleeper) error {
-	var retryer Retryer
-	for {
-		err := call(ctx, settings)
-		if err == nil {
-			return nil
-		}
-		if settings.Retry == nil {
-			return err
-		}
-		if retryer == nil {
-			if r := settings.Retry(); r != nil {
-				retryer = r
-			} else {
-				return err
-			}
-		}
-		if d, ok := retryer.Retry(err); !ok {
-			return err
-		} else if err = sp(ctx, d); err != nil {
-			return err
-		}
-	}
+	return v2.Sleep(ctx, d)
 }
diff --git a/invoke_test.go b/invoke_test.go
deleted file mode 100644
index d476d14..0000000
--- a/invoke_test.go
+++ /dev/null
@@ -1,155 +0,0 @@
-// Copyright 2016, Google Inc.
-// All rights reserved.
-//
-// Redistribution and use in source and binary forms, with or without
-// modification, are permitted provided that the following conditions are
-// met:
-//
-//     * Redistributions of source code must retain the above copyright
-// notice, this list of conditions and the following disclaimer.
-//     * Redistributions in binary form must reproduce the above
-// copyright notice, this list of conditions and the following disclaimer
-// in the documentation and/or other materials provided with the
-// distribution.
-//     * Neither the name of Google Inc. nor the names of its
-// contributors may be used to endorse or promote products derived from
-// this software without specific prior written permission.
-//
-// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-package gax
-
-import (
-	"context"
-	"errors"
-	"testing"
-	"time"
-)
-
-var canceledContext context.Context
-
-func init() {
-	ctx, cancel := context.WithCancel(context.Background())
-	cancel()
-	canceledContext = ctx
-}
-
-// recordSleeper is a test implementation of sleeper.
-type recordSleeper int
-
-func (s *recordSleeper) sleep(ctx context.Context, _ time.Duration) error {
-	*s++
-	return ctx.Err()
-}
-
-type boolRetryer bool
-
-func (r boolRetryer) Retry(err error) (time.Duration, bool) { return 0, bool(r) }
-
-func TestInvokeSuccess(t *testing.T) {
-	apiCall := func(context.Context, CallSettings) error { return nil }
-	var sp recordSleeper
-	err := invoke(context.Background(), apiCall, CallSettings{}, sp.sleep)
-
-	if err != nil {
-		t.Errorf("found error %s, want nil", err)
-	}
-	if sp != 0 {
-		t.Errorf("slept %d times, should not have slept since the call succeeded", int(sp))
-	}
-}
-
-func TestInvokeNoRetry(t *testing.T) {
-	apiErr := errors.New("foo error")
-	apiCall := func(context.Context, CallSettings) error { return apiErr }
-	var sp recordSleeper
-	err := invoke(context.Background(), apiCall, CallSettings{}, sp.sleep)
-
-	if err != apiErr {
-		t.Errorf("found error %s, want %s", err, apiErr)
-	}
-	if sp != 0 {
-		t.Errorf("slept %d times, should not have slept since retry is not specified", int(sp))
-	}
-}
-
-func TestInvokeNilRetry(t *testing.T) {
-	apiErr := errors.New("foo error")
-	apiCall := func(context.Context, CallSettings) error { return apiErr }
-	var settings CallSettings
-	WithRetry(func() Retryer { return nil }).Resolve(&settings)
-	var sp recordSleeper
-	err := invoke(context.Background(), apiCall, settings, sp.sleep)
-
-	if err != apiErr {
-		t.Errorf("found error %s, want %s", err, apiErr)
-	}
-	if sp != 0 {
-		t.Errorf("slept %d times, should not have slept since retry is not specified", int(sp))
-	}
-}
-
-func TestInvokeNeverRetry(t *testing.T) {
-	apiErr := errors.New("foo error")
-	apiCall := func(context.Context, CallSettings) error { return apiErr }
-	var settings CallSettings
-	WithRetry(func() Retryer { return boolRetryer(false) }).Resolve(&settings)
-	var sp recordSleeper
-	err := invoke(context.Background(), apiCall, settings, sp.sleep)
-
-	if err != apiErr {
-		t.Errorf("found error %s, want %s", err, apiErr)
-	}
-	if sp != 0 {
-		t.Errorf("slept %d times, should not have slept since retry is not specified", int(sp))
-	}
-}
-
-func TestInvokeRetry(t *testing.T) {
-	const target = 3
-
-	retryNum := 0
-	apiErr := errors.New("foo error")
-	apiCall := func(context.Context, CallSettings) error {
-		retryNum++
-		if retryNum < target {
-			return apiErr
-		}
-		return nil
-	}
-	var settings CallSettings
-	WithRetry(func() Retryer { return boolRetryer(true) }).Resolve(&settings)
-	var sp recordSleeper
-	err := invoke(context.Background(), apiCall, settings, sp.sleep)
-
-	if err != nil {
-		t.Errorf("found error %s, want nil, call should have succeeded after %d tries", err, target)
-	}
-	if sp != target-1 {
-		t.Errorf("retried %d times, want %d", int(sp), int(target-1))
-	}
-}
-
-func TestInvokeRetryTimeout(t *testing.T) {
-	apiErr := errors.New("foo error")
-	apiCall := func(context.Context, CallSettings) error { return apiErr }
-	var settings CallSettings
-	WithRetry(func() Retryer { return boolRetryer(true) }).Resolve(&settings)
-	var sp recordSleeper
-
-	err := invoke(canceledContext, apiCall, settings, sp.sleep)
-
-	if err != context.Canceled {
-		t.Errorf("found error %s, want %s", err, context.Canceled)
-	}
-}
diff --git a/v2/gax.go b/v2/gax.go
index 8b2900e..3191586 100644
--- a/v2/gax.go
+++ b/v2/gax.go
@@ -35,4 +35,4 @@
 // to simplify code generation and to provide more convenient and idiomatic API surfaces.
 package gax
 
-const Version = "2.0.0"
+const Version = "2.0.1"