startSpan(name, opts) {
		let span;
		if (this.span) {
			span = this.span.startSpan(name, Object.assign({ ctx: this }, opts));
		} else {
			span = this.broker.tracer.startSpan(name, Object.assign({ ctx: this }, opts));
		}

		this._spanStack.push(span);
		this.span = span;

		return span;
	}
Start a new child tracing span.

@param {String} name
@param {Object?} opts
@returns {Span}
@memberof Context