20191215 code improvements (#790)

* Upgrade godo to latest
* Fix a bunch of issues found by
* Running staticcheck on a codebase for the first time is a sobering experience
* go mod tidy
* More static improvements

Signed-off-by: Chris Cummer <chriscummer@me.com>

modules/twitterstats/client.go

@@ -16,7 +16,6 @@ import (
 type Client struct {
 	httpClient  *http.Client
 	screenNames []string
-	bearerToken string
 }
 
 // TwitterStats Represents a stats snapshot for a single Twitter user at a point in time
@@ -48,7 +47,7 @@ func NewClient(settings *Settings) *Client {
 			ClientSecret: settings.consumerSecret,
 			TokenURL:     "https://api.twitter.com/oauth2/token",
 		}
-		httpClient = conf.Client(oauth2.NoContext)
+		httpClient = conf.Client(context.Background())
 	} else {
 		ctx := context.Background()
 		httpClient = oauth2.NewClient(ctx, oauth2.StaticTokenSource(&oauth2.Token{