all: imp docs

internal/bootstrap/bootstrap.go

@@ -129,7 +129,6 @@ func NewDialContext(timeout time.Duration, addrs ...string) (h DialHandler) {
 			return conn, nil
 		}
 
-		// TODO(e.burkov):  Use errors.Join in Go 1.20.
-		return nil, errors.List("all dialers failed", errs...)
+		return nil, errors.Join(errs...)
 	}
 }

upstream/resolver.go

@@ -205,7 +205,7 @@ func (r *UpstreamResolver) resolveIP(
 
 // resolve performs a single DNS lookup of host and returns all the valid
 // addresses from the answer section of the response.  network must be either
-// "ip4" or "ip6".
+// "ip4" or "ip6".  host must be in a lower-case FQDN form.
 //
 // TODO(e.burkov):  Consider NS and Extra sections when setting TTL.  Check out
 // what RFCs say about it.
@@ -235,8 +235,10 @@ func (r *UpstreamResolver) resolve(
 		}},
 	}
 
+	// As per [upstream.Exchange] documentation, the response is always returned
+	// if no error occurred.
 	resp, err := r.Exchange(req)
-	if err != nil || resp == nil {
+	if err != nil {
 		return nil, err
 	}