code: func (t *Tracing) StartSpanf(r *http.Request, spanKind ext.SpanKindEnum, opPrefix string, opParts []string, separator string, opts ...opentracing.StartSpanOption) (opentracing.Span, *http.Request, func()) {
  	operationName := generateOperationName(opPrefix, opParts, separator, t.SpanNameLimit)
  
  	return StartSpan(r, operationName, spanKind, opts...)
  }
docs: // StartSpanf delegates to StartSpan.