Feature request: Improve the message for case when tags are omitted in structs' field types

[Antonboom]

it was a long journey to figure out what exactly linter was unhappy with :)

Simple example:

type AddUsersResponse struct {
	Seq     int                     `json:"seq,omitempty"`
	Succeed []int                   `json:"succeed,omitempty"`
	Errors  []AddUsersResponseError `json:"errors,omitempty"`
}

type AddUsersResponseError struct {
	ChatID int               // <----
	ErrMsg string         // <----
}

resp := new(AddUsersResponse)
json.NewEncoder(w).Encode(resp)

[tmzane]

Yep, it's a known problem :)

We've got #89 to solve this, but I'm still not sure which implementation would be better. Suggestions are welcome!