Fix data race surrounding Client.Rate.

Previously, concurrent calls to Client.Do would have data races writing
Client.Rate. Protect it with a mutex.

Resolves #253.

github/github.go

@@ -17,6 +17,7 @@ import (
 	"reflect"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/google/go-querystring/query"
@@ -64,11 +65,8 @@ type Client struct {
 	// User agent used when communicating with the GitHub API.
 	UserAgent string
 
-	// Rate specifies the current rate limit for the client as determined by the
-	// most recent API call.  If the client is used in a multi-user application,
-	// this rate may not always be up-to-date.  Call RateLimits() to check the
-	// current rate.
-	Rate Rate
+	rateMu sync.Mutex
+	rate   Rate
 
 	// Services used for talking to different parts of the GitHub API.
 	Activity      *ActivityService
@@ -292,6 +290,17 @@ func (r *Response) populateRate() {
 	}
 }
 
+// Rate specifies the current rate limit for the client as determined by the
+// most recent API call.  If the client is used in a multi-user application,
+// this rate may not always be up-to-date.  Call RateLimits() to check the
+// current rate.
+func (c *Client) Rate() Rate {
+	c.rateMu.Lock()
+	rate := c.rate
+	c.rateMu.Unlock()
+	return rate
+}
+
 // Do sends an API request and returns the API response.  The API response is
 // JSON decoded and stored in the value pointed to by v, or returned as an
 // error if an API error has occurred.  If v implements the io.Writer
@@ -307,7 +316,9 @@ func (c *Client) Do(req *http.Request, v interface{}) (*Response, error) {
 
 	response := newResponse(resp)
 
-	c.Rate = response.Rate
+	c.rateMu.Lock()
+	c.rate = response.Rate
+	c.rateMu.Unlock()
 
 	err = CheckResponse(resp)
 	if err != nil {

github/github_test.go

@@ -378,28 +378,28 @@ func TestDo_rateLimit(t *testing.T) {
 		w.Header().Add(headerRateReset, "1372700873")
 	})
 
-	if got, want := client.Rate.Limit, 0; got != want {
+	if got, want := client.Rate().Limit, 0; got != want {
 		t.Errorf("Client rate limit = %v, want %v", got, want)
 	}
-	if got, want := client.Rate.Remaining, 0; got != want {
+	if got, want := client.Rate().Remaining, 0; got != want {
 		t.Errorf("Client rate remaining = %v, got %v", got, want)
 	}
-	if !client.Rate.Reset.IsZero() {
+	if !client.Rate().Reset.IsZero() {
 		t.Errorf("Client rate reset not initialized to zero value")
 	}
 
 	req, _ := client.NewRequest("GET", "/", nil)
 	client.Do(req, nil)
 
-	if got, want := client.Rate.Limit, 60; got != want {
+	if got, want := client.Rate().Limit, 60; got != want {
 		t.Errorf("Client rate limit = %v, want %v", got, want)
 	}
-	if got, want := client.Rate.Remaining, 59; got != want {
+	if got, want := client.Rate().Remaining, 59; got != want {
 		t.Errorf("Client rate remaining = %v, want %v", got, want)
 	}
 	reset := time.Date(2013, 7, 1, 17, 47, 53, 0, time.UTC)
-	if client.Rate.Reset.UTC() != reset {
-		t.Errorf("Client rate reset = %v, want %v", client.Rate.Reset, reset)
+	if client.Rate().Reset.UTC() != reset {
+		t.Errorf("Client rate reset = %v, want %v", client.Rate().Reset, reset)
 	}
 }
 
@@ -418,15 +418,15 @@ func TestDo_rateLimit_errorResponse(t *testing.T) {
 	req, _ := client.NewRequest("GET", "/", nil)
 	client.Do(req, nil)
 
-	if got, want := client.Rate.Limit, 60; got != want {
+	if got, want := client.Rate().Limit, 60; got != want {
 		t.Errorf("Client rate limit = %v, want %v", got, want)
 	}
-	if got, want := client.Rate.Remaining, 59; got != want {
+	if got, want := client.Rate().Remaining, 59; got != want {
 		t.Errorf("Client rate remaining = %v, want %v", got, want)
 	}
 	reset := time.Date(2013, 7, 1, 17, 47, 53, 0, time.UTC)
-	if client.Rate.Reset.UTC() != reset {
-		t.Errorf("Client rate reset = %v, want %v", client.Rate.Reset, reset)
+	if client.Rate().Reset.UTC() != reset {
+		t.Errorf("Client rate reset = %v, want %v", client.Rate().Reset, reset)
 	}
 }
 
@@ -453,7 +453,7 @@ func TestCheckResponse(t *testing.T) {
 	res := &http.Response{
 		Request:    &http.Request{},
 		StatusCode: http.StatusBadRequest,
-		Body: ioutil.NopCloser(strings.NewReader(`{"message":"m", 
+		Body: ioutil.NopCloser(strings.NewReader(`{"message":"m",
 			"errors": [{"resource": "r", "field": "f", "code": "c"}]}`)),
 	}
 	err := CheckResponse(res).(*ErrorResponse)