finishSpan(span, time) {
		if (!span.isActive()) return;

		span.finish(time);

		const idx = this._spanStack.findIndex(sp => sp == span);
		if (idx !== -1) {
			this._spanStack.splice(idx, 1);
			this.span = this._spanStack[this._spanStack.length - 1];
		} else {
			/* istanbul ignore next */
			this.service.logger.warn("This span is not assigned to this context", span);
		}
	}
Finish an active span.

@param {Span} span
@param {Number?} time