raft/status.go
func (s Status) MarshalJSON() ([]byte, error) {
	j := fmt.Sprintf(`{"id":"%x","term":%d,"vote":"%x","commit":%d,"lead":"%x","raftState":%q,"applied":%d,"progress":{`,
		s.ID, s.Term, s.Vote, s.Commit, s.Lead, s.RaftState, s.Applied)

	if len(s.Progress) == 0 {
		j += "},"
	} else {
		for k, v := range s.Progress {
			subj := fmt.Sprintf(`"%x":{"match":%d,"next":%d,"state":%q},`, k, v.Match, v.Next, v.State)
			j += subj
		}
		// remove the trailing ","
		j = j[:len(j)-1] + "},"
	}

	j += fmt.Sprintf(`"leadtransferee":"%x"}`, s.LeadTransferee)
	return []byte(j), nil
}
func (s Status) MarshalJSON() ([]byte, error) {
	j := fmt.Sprintf(`{"id":"%x","term":%d,"vote":"%x","commit":%d,"lead":"%x","raftState":%q,"applied":%d,"progress":{`,
		s.ID, s.Term, s.Vote, s.Commit, s.Lead, s.RaftState, s.Applied)

	if len(s.Progress) == 0 {
		j += "},"
	} else {
		for k, v := range s.Progress {
			subj := fmt.Sprintf(`"%x":{"match":%d,"next":%d,"state":%q},`, k, v.Match, v.Next, v.State)
			j += subj
		}
		// remove the trailing ","
		j = j[:len(j)-1] + "},"
	}

	j += fmt.Sprintf(`"leadtransferee":"%x"}`, s.LeadTransferee)
	return []byte(j), nil
}
// MarshalJSON translates the raft status into JSON.
// TODO: try to simplify this by introducing ID type into raft