diff --git a/vendor/golang.org/x/oauth2/token.go b/vendor/golang.org/x/oauth2/token.go
new file mode 100644
index 0000000..ee4be54
--- /dev/null
+++ b/vendor/golang.org/x/oauth2/token.go
@@ -0,0 +1,178 @@
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package oauth2
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.org/x/oauth2/internal"
+)
+
+// expiryDelta determines how earlier a token should be considered
+// expired than its actual expiration time. It is used to avoid late
+// expirations due to client-server time mismatches.
+const expiryDelta = 10 * time.Second
+
+// Token represents the credentials used to authorize
+// the requests to access protected resources on the OAuth 2.0
+// provider's backend.
+//
+// Most users of this package should not access fields of Token
+// directly. They're exported mostly for use by related packages
+// implementing derivative OAuth2 flows.
+type Token struct {
+	// AccessToken is the token that authorizes and authenticates
+	// the requests.
+	AccessToken string `json:"access_token"`
+
+	// TokenType is the type of token.
+	// The Type method returns either this or "Bearer", the default.
+	TokenType string `json:"token_type,omitempty"`
+
+	// RefreshToken is a token that's used by the application
+	// (as opposed to the user) to refresh the access token
+	// if it expires.
+	RefreshToken string `json:"refresh_token,omitempty"`
+
+	// Expiry is the optional expiration time of the access token.
+	//
+	// If zero, TokenSource implementations will reuse the same
+	// token forever and RefreshToken or equivalent
+	// mechanisms for that TokenSource will not be used.
+	Expiry time.Time `json:"expiry,omitempty"`
+
+	// raw optionally contains extra metadata from the server
+	// when updating a token.
+	raw interface{}
+}
+
+// Type returns t.TokenType if non-empty, else "Bearer".
+func (t *Token) Type() string {
+	if strings.EqualFold(t.TokenType, "bearer") {
+		return "Bearer"
+	}
+	if strings.EqualFold(t.TokenType, "mac") {
+		return "MAC"
+	}
+	if strings.EqualFold(t.TokenType, "basic") {
+		return "Basic"
+	}
+	if t.TokenType != "" {
+		return t.TokenType
+	}
+	return "Bearer"
+}
+
+// SetAuthHeader sets the Authorization header to r using the access
+// token in t.
+//
+// This method is unnecessary when using Transport or an HTTP Client
+// returned by this package.
+func (t *Token) SetAuthHeader(r *http.Request) {
+	r.Header.Set("Authorization", t.Type()+" "+t.AccessToken)
+}
+
+// WithExtra returns a new Token that's a clone of t, but using the
+// provided raw extra map. This is only intended for use by packages
+// implementing derivative OAuth2 flows.
+func (t *Token) WithExtra(extra interface{}) *Token {
+	t2 := new(Token)
+	*t2 = *t
+	t2.raw = extra
+	return t2
+}
+
+// Extra returns an extra field.
+// Extra fields are key-value pairs returned by the server as a
+// part of the token retrieval response.
+func (t *Token) Extra(key string) interface{} {
+	if raw, ok := t.raw.(map[string]interface{}); ok {
+		return raw[key]
+	}
+
+	vals, ok := t.raw.(url.Values)
+	if !ok {
+		return nil
+	}
+
+	v := vals.Get(key)
+	switch s := strings.TrimSpace(v); strings.Count(s, ".") {
+	case 0: // Contains no "."; try to parse as int
+		if i, err := strconv.ParseInt(s, 10, 64); err == nil {
+			return i
+		}
+	case 1: // Contains a single "."; try to parse as float
+		if f, err := strconv.ParseFloat(s, 64); err == nil {
+			return f
+		}
+	}
+
+	return v
+}
+
+// timeNow is time.Now but pulled out as a variable for tests.
+var timeNow = time.Now
+
+// expired reports whether the token is expired.
+// t must be non-nil.
+func (t *Token) expired() bool {
+	if t.Expiry.IsZero() {
+		return false
+	}
+	return t.Expiry.Round(0).Add(-expiryDelta).Before(timeNow())
+}
+
+// Valid reports whether t is non-nil, has an AccessToken, and is not expired.
+func (t *Token) Valid() bool {
+	return t != nil && t.AccessToken != "" && !t.expired()
+}
+
+// tokenFromInternal maps an *internal.Token struct into
+// a *Token struct.
+func tokenFromInternal(t *internal.Token) *Token {
+	if t == nil {
+		return nil
+	}
+	return &Token{
+		AccessToken:  t.AccessToken,
+		TokenType:    t.TokenType,
+		RefreshToken: t.RefreshToken,
+		Expiry:       t.Expiry,
+		raw:          t.Raw,
+	}
+}
+
+// retrieveToken takes a *Config and uses that to retrieve an *internal.Token.
+// This token is then mapped from *internal.Token into an *oauth2.Token which is returned along
+// with an error..
+func retrieveToken(ctx context.Context, c *Config, v url.Values) (*Token, error) {
+	tk, err := internal.RetrieveToken(ctx, c.ClientID, c.ClientSecret, c.Endpoint.TokenURL, v)
+	if err != nil {
+		if rErr, ok := err.(*internal.RetrieveError); ok {
+			return nil, (*RetrieveError)(rErr)
+		}
+		return nil, err
+	}
+	return tokenFromInternal(tk), nil
+}
+
+// RetrieveError is the error returned when the token endpoint returns a
+// non-2XX HTTP status code.
+type RetrieveError struct {
+	Response *http.Response
+	// Body is the body that was consumed by reading Response.Body.
+	// It may be truncated.
+	Body []byte
+}
+
+func (r *RetrieveError) Error() string {
+	return fmt.Sprintf("oauth2: cannot fetch token: %v\nResponse: %s", r.Response.Status, r.Body)
+}