The total time in trace info may become MAX_INT64 in some invalid requests

[git-hulk]

Currently, the request total is calculated by EndTime - DNS Start Time | Get Conn Time:

resty/request.go

Lines 1256 to 1260 in 036c589

	if ct.gotConnInfo.Reused {
	ti.TotalTime = ct.endTime.Sub(ct.getConn)
	} else {
	ti.TotalTime = ct.endTime.Sub(ct.dnsStart)
	}

And in Go's transport, it won't call the GetConn if the request is invalid(for example: an invalid URL format), so both of DNS Start Time | Get Conn Time are zero. So it will get MAX_INT64 if we use a valid time to sub the zero time.