code: func (c *Config) Setup(serviceName string) (opentracing.Tracer, io.Closer, error) {
  	// set default logLevel
  	logLevel := instana.Info
  
  	// check/set logLevel overrides
  	switch c.LogLevel {
  	case "error":
  		logLevel = instana.Error
  	case "warn":
  		logLevel = instana.Warn
  	case "debug":
  		logLevel = instana.Debug
  	}
  
  	tracer := instana.NewTracerWithOptions(&instana.Options{
  		Service:   serviceName,
  		LogLevel:  logLevel,
  		AgentPort: c.LocalAgentPort,
  		AgentHost: c.LocalAgentHost,
  	})
  
  	// Without this, child spans are getting the NOOP tracer
  	opentracing.SetGlobalTracer(tracer)
  
  	log.WithoutContext().Debug("Instana tracer configured")
  
  	return tracer, nil, nil
  }
docs: // Setup sets up the tracer