opentracing: Unknown or unsupported Inject/Extract format

[dayadev]

I am working on a grpc service using the grpc-opentracing interceptor in one of my projects at https://github.com/dayadev/grpc-zipkin-with-grpc-gateway
but not able to extract span from the parent context and hence unable to propagate trace ids in inter service communication and I think when grpc_opentracing.UnaryServerInterceptor(grpc_opentracing.WithTracer(tracer) is invoked on a request, inside the open tracing interceptor, opentracing: Unknown or unsupported Inject/Extract format while extracting the parent context span from the tracer at tracer.Extract(opentracing.HTTPHeaders, metadataTextMap(md))

What would be the issue in my code?