Use %+v instead of %#v when recovering panics

Many common panic values, e.g. nil pointer dereferences, don't print
very well under "%#v", emitting something like
"runtime.errorCString{cstr:0x54b2a4}" or similar.

web/middleware/recoverer.go

@@ -38,7 +38,7 @@ func printPanic(reqID string, err interface{}) {
 	if reqID != "" {
 		cW(&buf, bBlack, "[%s] ", reqID)
 	}
-	cW(&buf, bRed, "panic: %#v", err)
+	cW(&buf, bRed, "panic: %+v", err)
 
 	log.Print(buf.String())
 }