diff --git a/internal/sdk/doc_test.go b/internal/sdk/doc_test.go
index 152fcb1..34678b3 100644
--- a/internal/sdk/doc_test.go
+++ b/internal/sdk/doc_test.go
@@ -1,7 +1,7 @@
 package sdk
 
 import (
-	"io/ioutil"
+	"io"
 	"net/http"
 )
 
@@ -35,7 +35,7 @@ func (f *FakeMultiHTTPClient) Do(request *http.Request) (*http.Response, error)
 
 func (f *FakeMultiHTTPClient) simulateServerReadingRequestBody(request *http.Request) {
 	if request.Body != nil {
-		body, _ := ioutil.ReadAll(request.Body)
+		body, _ := io.ReadAll(request.Body)
 		f.bodies = append(f.bodies, string(body))
 	} else {
 		f.bodies = append(f.bodies, request.URL.Query().Get("body"))
diff --git a/internal/sdk/http_sender.go b/internal/sdk/http_sender.go
index bfe18e6..440bf84 100644
--- a/internal/sdk/http_sender.go
+++ b/internal/sdk/http_sender.go
@@ -1,7 +1,7 @@
 package sdk
 
 import (
-	"io/ioutil"
+	"io"
 	"net/http"
 
 	"github.com/smartystreets/smartystreets-go-sdk"
@@ -38,7 +38,7 @@ func readResponseBody(response *http.Response) ([]byte, error) {
 	// TODO: Since we already copy response.Body in retry_client.go -> readBody()
 	//       It would behoove us to prevent a second copy in that case.
 
-	if content, err := ioutil.ReadAll(response.Body); err != nil {
+	if content, err := io.ReadAll(response.Body); err != nil {
 		_ = response.Body.Close()
 		return nil, err
 	} else {
diff --git a/internal/sdk/keep_alive_close_client_test.go b/internal/sdk/keep_alive_close_client_test.go
index f61bd4b..bebf84d 100644
--- a/internal/sdk/keep_alive_close_client_test.go
+++ b/internal/sdk/keep_alive_close_client_test.go
@@ -1,7 +1,7 @@
 package sdk
 
 import (
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -26,7 +26,7 @@ func (f *KeepAliveCloseClientFixture) Setup() {
 	f.inner.response = &http.Response{
 		ProtoMajor: 1, ProtoMinor: 1,
 		StatusCode: http.StatusTeapot,
-		Body:       ioutil.NopCloser(strings.NewReader("Goodbye, World!")),
+		Body:       io.NopCloser(strings.NewReader("Goodbye, World!")),
 	}
 	f.request = httptest.NewRequest("GET", "/", nil)
 }
diff --git a/internal/sdk/retry_client.go b/internal/sdk/retry_client.go
index 82d4adb..55508ce 100644
--- a/internal/sdk/retry_client.go
+++ b/internal/sdk/retry_client.go
@@ -3,7 +3,6 @@ package sdk
 import (
 	"bytes"
 	"io"
-	"io/ioutil"
 	"math/rand"
 	"net/http"
 	"sync"
@@ -54,13 +53,13 @@ func (r *RetryClient) doGet(request *http.Request) (response *http.Response, err
 }
 
 func (r *RetryClient) doBufferedPost(request *http.Request) (response *http.Response, err error) {
-	body, err := ioutil.ReadAll(request.Body)
+	body, err := io.ReadAll(request.Body)
 	if err != nil {
 		return nil, err
 	}
 
 	for attempt := 0; r.backOff(attempt); attempt++ {
-		request.Body = ioutil.NopCloser(bytes.NewReader(body))
+		request.Body = io.NopCloser(bytes.NewReader(body))
 		if response, err = r.inner.Do(request); err == nil && response.StatusCode == http.StatusOK {
 			if r.readBody(response) {
 				break
@@ -82,6 +81,7 @@ func (r *RetryClient) handleHttpStatusCode(response *http.Response, attempt *int
 	}
 	if response.StatusCode == http.StatusTooManyRequests {
 		r.sleeper(time.Second * time.Duration(r.random(backOffRateLimit)))
+		// Setting attempt to 1 will make 429s retry indefinitely; this is intended behavior.
 		*attempt = 1
 	}
 	return true
diff --git a/us-autocomplete-pro-api/lookup.go b/us-autocomplete-pro-api/lookup.go
index 227531d..b43d0ae 100644
--- a/us-autocomplete-pro-api/lookup.go
+++ b/us-autocomplete-pro-api/lookup.go
@@ -22,6 +22,7 @@ type (
 		PreferZIP     []string
 		PreferRatio   int
 		Geolocation   Geolocation
+		Selected      string
 
 		Results []*Suggestion
 	}
@@ -46,6 +47,7 @@ func (l Lookup) populate(query url.Values) {
 	l.populatePreferRatio(query)
 	l.populateGeolocation(query)
 	l.populateSource(query)
+	l.populateSelected(query)
 }
 
 func (l Lookup) populateSearch(query url.Values) {
@@ -116,3 +118,8 @@ func (l Lookup) populateSource(query url.Values) {
 		query.Set("source", l.Source)
 	}
 }
+func (l Lookup) populateSelected(query url.Values) {
+	if len(l.Selected) > 0 {
+		query.Set("selected", l.Selected)
+	}
+}
diff --git a/us-autocomplete-pro-api/lookup_test.go b/us-autocomplete-pro-api/lookup_test.go
index 70b68e8..e1273d4 100644
--- a/us-autocomplete-pro-api/lookup_test.go
+++ b/us-autocomplete-pro-api/lookup_test.go
@@ -147,3 +147,12 @@ func (f *LookupSerializationFixture) TestGeolocateCity_DefaultValue() {
 	f.So(f.query, should.HaveLength, 1)
 	f.So(f.query.Get("prefer_geolocation"), should.Equal, "city")
 }
+
+func (f *LookupSerializationFixture) TestSelect() {
+	f.lookup.Selected = "Hello World!"
+
+	f.populate()
+
+	f.So(f.query, should.HaveLength, 1)
+	f.So(f.query.Get("selected"), should.Equal, "Hello World!")
+}
diff --git a/us-extract-api/lookup.go b/us-extract-api/lookup.go
index bb9bd68..4ecb29e 100644
--- a/us-extract-api/lookup.go
+++ b/us-extract-api/lookup.go
@@ -1,11 +1,12 @@
 package extract
 
 import (
-	"github.com/smartystreets/smartystreets-go-sdk/us-street-api"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strconv"
 	"strings"
+
+	"github.com/smartystreets/smartystreets-go-sdk/us-street-api"
 )
 
 // Lookup represents all input fields documented here:
@@ -64,7 +65,7 @@ func (l *Lookup) setBody(request *http.Request) {
 	}
 
 	body := strings.NewReader(l.Text)
-	request.Body = ioutil.NopCloser(body)
+	request.Body = io.NopCloser(body)
 	request.ContentLength = int64(body.Len())
 }
 func (l *Lookup) setHeaders(request *http.Request) {
diff --git a/us-extract-api/lookup_test.go b/us-extract-api/lookup_test.go
index 7e15954..3facef5 100644
--- a/us-extract-api/lookup_test.go
+++ b/us-extract-api/lookup_test.go
@@ -1,7 +1,7 @@
 package extract
 
 import (
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"testing"
@@ -33,7 +33,7 @@ func (f *LookupFixture) query() url.Values {
 }
 
 func readBody(request *http.Request) string {
-	bytes, _ := ioutil.ReadAll(request.Body)
+	bytes, _ := io.ReadAll(request.Body)
 	return string(bytes)
 }
 
diff --git a/us-street-api/batch.go b/us-street-api/batch.go
index 8b0ea30..6498bbc 100644
--- a/us-street-api/batch.go
+++ b/us-street-api/batch.go
@@ -3,7 +3,7 @@ package street
 import (
 	"bytes"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 )
 
@@ -79,7 +79,7 @@ func (b *Batch) serializeGET(request *http.Request) {
 func (b *Batch) serializePOST(request *http.Request) {
 	request.Method = http.MethodPost
 	payload, _ := json.Marshal(b.lookups) // We control the types being serialized. This is safe.
-	request.Body = ioutil.NopCloser(bytes.NewReader(payload))
+	request.Body = io.NopCloser(bytes.NewReader(payload))
 	request.ContentLength = int64(len(payload))
 	request.Header.Set("Content-Type", "application/json")
 }
diff --git a/us-street-api/batch_processing_test.go b/us-street-api/batch_processing_test.go
index 8d88796..586a674 100644
--- a/us-street-api/batch_processing_test.go
+++ b/us-street-api/batch_processing_test.go
@@ -3,7 +3,7 @@ package street
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strconv"
 	"testing"
@@ -130,7 +130,7 @@ func (f *FakeMultiSender) Send(request *http.Request) ([]byte, error) {
 	f.requests = append(f.requests, request)
 
 	if request.Body != nil {
-		body, _ := ioutil.ReadAll(request.Body)
+		body, _ := io.ReadAll(request.Body)
 		f.requestBodies = append(f.requestBodies, string(body))
 	}
 
diff --git a/us-street-api/client_test.go b/us-street-api/client_test.go
index 4b0394f..eb34944 100644
--- a/us-street-api/client_test.go
+++ b/us-street-api/client_test.go
@@ -3,7 +3,7 @@ package street
 import (
 	"context"
 	"errors"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"testing"
@@ -292,7 +292,7 @@ func (f *FakeSender) Send(request *http.Request) ([]byte, error) {
 	f.callCount++
 	f.request = request
 	if request != nil && request.Body != nil {
-		f.requestBody, _ = ioutil.ReadAll(request.Body)
+		f.requestBody, _ = io.ReadAll(request.Body)
 	}
 	return []byte(f.response), f.err
 }
diff --git a/us-zipcode-api/batch.go b/us-zipcode-api/batch.go
index 51c8c03..ac02c01 100644
--- a/us-zipcode-api/batch.go
+++ b/us-zipcode-api/batch.go
@@ -3,7 +3,7 @@ package zipcode
 import (
 	"bytes"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"net/http"
 )
 
@@ -77,7 +77,7 @@ func (b *Batch) serializeGET(request *http.Request) {
 func (b *Batch) serializePOST(request *http.Request) {
 	request.Method = http.MethodPost
 	payload, _ := json.Marshal(b.lookups) // We control the types being serialized. This is safe.
-	request.Body = ioutil.NopCloser(bytes.NewReader(payload))
+	request.Body = io.NopCloser(bytes.NewReader(payload))
 	request.ContentLength = int64(len(payload))
 	request.Header.Set("Content-Type", "application/json")
 }
diff --git a/us-zipcode-api/batch_processing_test.go b/us-zipcode-api/batch_processing_test.go
index 1dc5937..a72cba8 100644
--- a/us-zipcode-api/batch_processing_test.go
+++ b/us-zipcode-api/batch_processing_test.go
@@ -3,7 +3,7 @@ package zipcode
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"strconv"
 	"testing"
@@ -130,7 +130,7 @@ func (f *FakeMultiSender) Send(request *http.Request) ([]byte, error) {
 	f.requests = append(f.requests, request)
 
 	if request.Body != nil {
-		body, _ := ioutil.ReadAll(request.Body)
+		body, _ := io.ReadAll(request.Body)
 		f.requestBodies = append(f.requestBodies, string(body))
 	}
 
diff --git a/us-zipcode-api/client_test.go b/us-zipcode-api/client_test.go
index 11cc1b9..8b576c7 100644
--- a/us-zipcode-api/client_test.go
+++ b/us-zipcode-api/client_test.go
@@ -3,7 +3,7 @@ package zipcode
 import (
 	"context"
 	"errors"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"testing"
@@ -133,7 +133,7 @@ func (f *FakeSender) Send(request *http.Request) ([]byte, error) {
 	f.callCount++
 	f.request = request
 	if request.Body != nil {
-		f.requestBody, _ = ioutil.ReadAll(request.Body)
+		f.requestBody, _ = io.ReadAll(request.Body)
 	}
 	return []byte(f.response), f.err
 }