reference global logrus (#274)

* reference logrus' global logger instead of passing and storing a logger reference everywhere

* always directly use global logrus logger instead of referencing an instance

* test suites should also directly use the global logrus logger

* rename gin logging function to clarify that it's middleware

* correct comments which erroneously referenced removed logger parameter

* setting log level for tests now uses logrus' exported type instead of the string value, to guarantee error isn't possible

internal/transport/finger.go

@@ -21,13 +21,14 @@ package transport
 import (
 	"context"
 	"fmt"
+	"github.com/sirupsen/logrus"
 	"io/ioutil"
 	"net/http"
 	"net/url"
 )
 
 func (t *transport) Finger(ctx context.Context, targetUsername string, targetDomain string) ([]byte, error) {
-	l := t.log.WithField("func", "Finger")
+	l := logrus.WithField("func", "Finger")
 	urlString := fmt.Sprintf("https://%s/.well-known/webfinger?resource=acct:%s@%s", targetDomain, targetUsername, targetDomain)
 	l.Debugf("performing GET to %s", urlString)