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/zendesk/client.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
-	"log"
 	"net/http"
 )
 
@@ -13,12 +12,6 @@ type Resource struct {
 	Raw      string
 }
 
-func errHandler(err error) {
-	if err != nil {
-		log.Print(err)
-	}
-}
-
 func (widget *Widget) api(meth string, path string, params string) (*Resource, error) {
 	trn := &http.Transport{}