slight style tweaks, use New and NewForWork, take a RoundTripper

backoff.go

@@ -7,16 +7,13 @@ import (
 )
 
 type backoff struct {
-	Transport *http.RoundTripper
+	Transport http.RoundTripper
 	MaxTries  int
 	tries     int
 	sleep     func(time.Duration)
 }
 
 func (bt *backoff) RoundTrip(req *http.Request) (*http.Response, error) {
-	if bt.Transport == nil {
-		bt.Transport = &http.DefaultTransport
-	}
 	if bt.MaxTries == 0 {
 		bt.MaxTries = 5
 	}
@@ -27,7 +24,7 @@ func (bt *backoff) RoundTrip(req *http.Request) (*http.Response, error) {
 	var err error
 	for ; bt.tries < bt.MaxTries; bt.tries++ {
 		var resp *http.Response
-		resp, err = (*bt.Transport).RoundTrip(req)
+		resp, err = bt.Transport.RoundTrip(req)
 		if err != nil {
 			// fallthrough, retry
 		} else if resp.StatusCode >= http.StatusInternalServerError {

backoff_test.go

@@ -15,7 +15,8 @@ func TestBackoff(t *testing.T) {
 	tries := 10
 	sleeps := 0
 	bt := &backoff{
-		MaxTries: tries,
+		MaxTries:  tries,
+		Transport: http.DefaultTransport,
 		sleep: func(d time.Duration) {
 			sleeps += 1
 			t.Logf("sleeping %s", d)

maps.go

@@ -52,21 +52,25 @@ type Client struct {
 	PrivateKey string
 }
 
-// NewClient returns a Client using the specified API key.
+// New returns a Client using the specified API key and RoundTripper.
-func NewClient(key string) Client {
+func New(key string, rt http.RoundTripper) Client {
-	return Client{Key: key, Transport: http.DefaultTransport}
+	return Client{Key: key, Transport: rt}
 }
 
-// NewWorkClient returns a Client using the specified Google Maps API for Work client ID and signature.
+// NewForWork returns a Client using the specified Google Maps API for Work client ID and signature, and RoundTripper.
 //
 // See https://developers.google.com/maps/documentation/business/
-func NewWorkClient(clientID, privateKey string) Client {
+func NewForWork(clientID, privateKey string, rt http.RoundTripper) Client {
-	return Client{ClientID: clientID, PrivateKey: privateKey, Transport: http.DefaultTransport}
+	return Client{ClientID: clientID, PrivateKey: privateKey, Transport: rt}
 }
 
 func (c Client) do(url string) (*http.Response, error) {
+	t := c.Transport
+	if t == nil {
+		t = http.DefaultTransport
+	}
 	cl := &http.Client{Transport: &backoff{
-		Transport: &c.Transport,
+		Transport: t,
 	}}
 	req, err := http.NewRequest("GET", url, nil)
 	if err != nil {

maps_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestDirections(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	orig, dest := Address("111 8th Ave, NYC"), Address("170 E 92nd St, NYC")
 	opts := &DirectionsOpts{
 		Mode:          ModeTransit,
@@ -22,7 +22,7 @@ func TestDirections(t *testing.T) {
 }
 
 func TestStaticMap(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	s := Size{512, 512}
 	opts := &StaticMapOpts{
 		Center: LatLng{-5, -5},
@@ -78,7 +78,7 @@ func TestStaticMap(t *testing.T) {
 }
 
 func TestStreetView(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	s := Size{600, 300}
 	opts := &StreetViewOpts{
 		Location: &LatLng{46.414382, 10.013988},
@@ -92,7 +92,7 @@ func TestStreetView(t *testing.T) {
 }
 
 func TestTimeZone(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	ll := LatLng{40.7142700, -74.0059700}
 	tm := time.Now()
 	t.Logf("%s", baseURL+timezone(ll, tm, nil))
@@ -104,7 +104,7 @@ func TestTimeZone(t *testing.T) {
 }
 
 func TestElevation(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	ll := []LatLng{{39.7391536, -104.9847034}}
 	t.Logf("%s", baseURL+elevation(ll))
 	r, err := c.Elevation(ll)
@@ -140,7 +140,7 @@ func TestElevation(t *testing.T) {
 }
 
 func TestGeocode(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	opts := &GeocodeOpts{
 		Address: Address("1600 Amphitheatre Parkway, Mountain View, CA"),
 	}
@@ -161,7 +161,7 @@ func TestGeocode(t *testing.T) {
 }
 
 func TestDistanceMatrix(t *testing.T) {
-	c := NewClient("")
+	c := New("", nil)
 	orig := []Location{Address("Vancouver, BC"), Address("Seattle")}
 	dst := []Location{Address("San Francisco"), Address("Victoria, BC")}
 	opts := &DistanceMatrixOpts{
@@ -179,7 +179,7 @@ func TestDistanceMatrix(t *testing.T) {
 
 // Based on https://developers.google.com/maps/documentation/business/webservices/auth#signature_examples
 func TestSignature(t *testing.T) {
-	c := NewWorkClient("", "vNIXE0xscrmjlyV-12Nj_BvUPaw=")
+	c := NewForWork("", "vNIXE0xscrmjlyV-12Nj_BvUPaw=", nil)
 	sig, err := c.genSig("/maps/api/geocode/json", "address=New+York&client=clientID")
 	if err != nil {
 		t.Errorf("unexpected error: %v", err)