oauth2: remove extra period

Change-Id: I369d3bed0e28427b1e1d416952c3766932ba3773
GitHub-Last-Rev: ca611fe
GitHub-Pull-Request: #724
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/587017
Auto-Submit: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Shin Fan <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: darkfeline

Diff for: token.go

@@ -169,7 +169,7 @@ func tokenFromInternal(t *internal.Token) *Token {
 
 // 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..
+// 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, internal.AuthStyle(c.Endpoint.AuthStyle), c.authStyleCache.Get())
 	if err != nil {